Lock offs aren't as big of a deal, at least for me, with a bucket. The few I've tried we're pretty easy to install without them, bases don't have issues with tipping and such like convertibles. You would only have to have them if you have a car that predates when seatbelt started locking, 1997 I think? And even then you can use a locking clip. I've installed the snugride (it was a 22 i think) with a seat belt in several different cars, its a cinch. Not chicco cinch, but not difficult at all. If you're were happy with all of the other features the lack of lock offs would by no means be a deal breaker for me (when you get to convertibles that's a whole different story :-o)
ETA: the bucket vs straight to convertible debate is really up to preference, it mainly comes down to if you like to baby wear or not. I personally would never skip the infant seat, because I'm not to keen on baby wearing, if you are, you could probably get away with skipping it. It's just so nice to have somewhere to sit the baby in a restaurant or doctors office, or to be able to take them in sleeping, or to be able to bundle them up when it's cold outside and just pop them in.