Okay, since nobody seems to have reviewed Citadel DLC here, I'll do it, since I've played through it a few days ago.
There's only one guideline: it's probably best to play this DLC from your final "pre-Cerberus-Base" save on the Normandy, because this way you'll get all the DLC's content at once.
You'll also get more content if you imported a ME2 save with all 12 squadmates, did good by Wrex and so on - an "ideal paragon" playthrough, in other words.
You've likely watched the video trailer or youtube walkthroughs, so the premise is familiar: Hackett orders some necessary maintenance/repairs for the Normandy, it's moved into dock, and you're getting mandatory shore leave on the Citadel. Anderson's conveniently gives you his Citadel apartment, because he, to quote Strugatsky brothers, now believes that "Earth is where the most important things are".
How realistic is it? Is it fair that Shep gets a great apartment while refugees in the wards struggle in squalor, and that Shepard and Co celebrate shore leave, as people die on Earth, Palaven and Dekuuna? I don't know, I've never been in real war, but I remember reading the Young Lions by Irwin Shaw some years ago about WW2, and I'd say it's quite plausible, at least the way Shaw wrote about it. There was shore leave, there was a chance to unwind, especially if you remembered what horrible places these soldiers came from. (By Jack's words, she comes back from battling husks on Palaven with her team and nearly losing one of her own - and I don't know about the others, but I think Jack deserved that leave tenfold). But anyway, I choose to believe that the mod's premise was more or less real(istic) - after all, Citadel still stands, restaurants still work and people still watch Blasto all around Shepard. And speaking of Blasto...
You're going to have GREAT one-on-one time with your squadmates. Javik, Vega&Cortez, romanced Garrus, non-romanced Miranda, Jack(non-romanced Jack and Miranda scenes for femShep are AWESOME), Joker, Grunt(I love you, Grunt!), Zaeed, Kasumi - frankly, nearly everyone. There's even audiovisual stuff from Thane and Mordin(no Legion, alas) - Thanemancers may or may not love the goodbye scene, but I think it was a good tribute. You can even hit Jacob(that cheater!) and he'll apologise!
And, yes, THE PARTY.
But before that, you're going to have a quest. For such a huge DLC, the quest is quite a short one. I won't spoil, but these are the main highlights: a sushi restaurant, a casino, a visit to the Citadel Archives, and a trip to the docks.
- You're getting LOTS of NPC reactions, including one from your romance interest. The quest *is* very short, however, and, unfortunately, in some places the pacing isn't done very well: for example, you're bombarded with NPC phrases and videoscenes from Citadel Archives too quickly, so you're likely to miss some of the good stuff.
- On the other hand, the pacing was slower in the casino, and I had every chance to enjoy every bit of random dialogue, but I didn't find it very good, even with the Consort(especially with her, actually).
- You're getting a Kasumi-like-mission, a break-in, but I didn't enjoy that part(too much intense micromanagement with security cameras for me, but I saw a guy posting that he loved it!);
- You're taking your whole ME3 crew with you to the Citadel Archives(no ME2 people, though), and it's cool, but, again, there's such thing as "too much good stuff" - you'll probably have to replay it a few times to catch all these brilliant blink and miss phrases.
- And, yep, there's a certain someone who wants not just to kill you and hijack your Normandy, but to PUT YOUR HAMSTER INTO AN ANIMAL SHELTER! Beware.
Once the mission is over, you're free to wander into the part of the Citadel outside your new apartment, play the many minigames(quasar!) in the Arcade and the casino, visit the Armax Arsenal arena(do it at least once to get an extra invitation for some quality time with Jack on the arena) and, most importantly, have some one-on-one time with your squadmates.
The latter is great. The former, I don't know - I am okay with minigames when they are sparse; this time, there were too many. And even though the developers added a nice touch "all your lost money go to the refugees", I'm afraid to say I didn't participate much. Besides, Shepard defeating an evil ***** and throwing a party - this I can understand. But Shepard wandering aimlessly for days in the arcade? The same Shepard who says "I'll sleep when I'm dead"? ... Um, that's a stretch here.
Multiplayer folks will probably enjoy various random dialogue outside your apartment, such as a banter about stupid vanguards who storm with mission packs(I assume you shouldn't?) and sentinels who do only one thing: detonate tech armor. Okay, I might be just grouchy, but I didn't enjoy that, either. Even Francis Kitt's appearance seemed a bit forced. Dancing with Garrus, though? Not at all!
(By the way, is it just me or did Garrus get TOO many females? Female Shepard, Doctor Michel, Tali, and now a female turian if you're not romancing him!)
Shopping: you can get new weapons and mods during the course of the quest(but my main pet peeve with ME3 still stands: you have to look for interactive objects very carefully, or you'll miss all this stuff).
Also, there's a shop that allows you to customize your apartment a bit(get nice couches instead of those awful Cerberus-styled black-and-white ones, for one). It doesn't have a big selection, but it was a nice touch.
And... and you get your love interest. From the initial comments after the failed sushi dinner with Joker to the "quality time-together"-scene to the party comments(Garrus's comment to Shepard dancing at the party! Aaaaargh!!), the after-party scene, the goodbye scene at the Normandy... I'll be banal here and repeat what several thousand people have already said: that goodbye scene from the Citadel DLC should be the real finale. And in a way, it was, it really was.
The party: you'll definitely want to replay it a few times, because the scenes change depending on your preference(you're only getting "Shepard! Wrex! Grunt!" scene in one of the choices, for one - I didn't get it in my party). It's got three stages, each stage a completely awesome work of love, and the aftermath. The aftermath is a marvel in itself, from Vega cooking eggs at the kitchen to waking up with your love interest(OR JAVIK, if your female isn't romancing anyone! OR even Vega, if you flirted with him and pressed him into a one-night stand!) - it was hilarious. Finding Javik in my bedroom's bathroom after I woke up with Garrus was, um, a worthy moment, too.
So, yep. Don't mind the sucking(sometimes) quest, don't mind the pacing, don't mind the cheese - I say it's worth it. You may even grow sentimental and buy Omega and Leviathan afterwards just to prolong the sensation. Because this truly is goodbye. And now that I've said it -
I should go. Or I *should* go? Or is it I should GO?