@Slipstream: That makes a lot of sense. I figure with the choice between classes and ladders you've already got a good bit of variety in the base. Knowing that there's additional things for them to do at low levels is going to be a big selling point for some folks. For more 'standard' games, I'd been house ruling in an additional at-will usable only as an Encounter power to throw in some variety without needing to worry much about balance or any real power creep, and that seemed pretty popular.
@bonenaga: Eh, I wasn't looking for a bump so much, (actually, I've been looking to avoid it as much as possible

) as just a way to give my players a bit more to do in the low level game. In general the 4e character doesn't have a full compliment (3E, 3D) of available choices until they're ready to hit paragon. The game is (mostly) built around that assumption, so it works, but it also results in a lot of the lower combat seeming a bit less dynamic to folks who've tasted those heady waters of high Heroic and beyond. I think the idea of using themes to replace the old feat-based multiclassing is a wonderful one for a number of reasons... outside of a few corner cases the return is never worth the expense, and just becomes another "choose absolutely right or suck" option for some of my players. Too many feats given up for too little gain--the first step feats, on the other hand, are pretty good, and I find myself using them almost constantly when I get to play.
Since I'm still not in the playtest group, I'm not wholly clear on how ladders and classes work in UM4/NS, so I can't comment to much on those other than "I like what I've heard."
COUGHSUPERSUBTLEHINTCOUGHAhem. Pardon me, summer colds are the wost.