There are two that I've just noticed. One is that the bomb will explicitly allow you to price out multi-city itineraries where the departure airport needn't be the same as the arrival airport from the previous leg (e.g. LAX-IAD, DCA-ORD, ORD-LAX). I always found this frustrating about the previous version of the site. Yes, I would sometimes see it pulling up such itineraries when pricing multi-city trips, but there wasn't a way, unless I missed something, to force the old .bomb to do this.

Another is that you are told an unambiguous time when holding a reservation. Instead of being told that my reservation would be held until midnight on December 12th, I was just told that it'll be held until 11:59pm on December 12th. I think the former is a questionable way to put it; the latter is obvious. (OK, that's not so much of a feature as it is a clarification, but that one always bugged me.)

There are still things about the booking engine that I don't like (the capability to see which flights are on sale, which was in the old version, has disappeared), but I think this engine is an improvement over the old one.

PS - Oh, yeah! This version allows one to search for *A flights ... not that I've seen it pull any up for me yet.