We have the keyfit 30 as well. Can't really give a detailed review or anything since we have only been using them for a couple of weeks, but so far they are great. Pretty lightweight, base is super easy to install and it's quick and easy snapping the seat in and out.
So the second kiddo has been home for a few days now, with the third hopefully coming home this Saturday. The whole time that we only had one home all I could think was how easy it was with just one. Two is bearable since one person can still handle both of them (feeding, changing, holding, etc.). Three is going to be really hard for the first month or two. I don't think we are going to be able to do shifts, pretty much all hands every couple of hours.
On the plus side, they are 37 weeks gestational age now and they are already approaching 6 pounds each. The preemie clothes no longer fit. One thing I wish I would have known was how much shit the NICU gives you. We have gotten like 50 bottles, 8 packs of diapers, 60 pre made formulas, a shit ton of desitin, nipples for every day of the year, about 15 pacifiers, plus more shit I can't remember. Oh and the pediatrician gave us 12 cans of Enfacare formula when we were there yesterday