I had the same concern, but as someone in the beta I think everything mostly looks mostly fine while you're playing and I'm not as concerned as I was after I got some games in. Still prefer the cleaner 2D of SC1, though.
Reapers are a good unit. Potential for some nice harass, something I think Protoss and Zerg are missing right now. At least the kind of exciting harass that say the reaver or potentially even a lurker drop provided in the first game.
I'm enjoying it right now and while it's far too early to tell if Blizzard will be able to get this game up to the legendary level of SC1 in regards to balance and having enough uniqueness to keep the game interesting for 12 years, if you liked the first game you will like the second one and certainly get your money's worth (I've probably played the beta longer than I have any other game in quite some time. Well, I probably haven't reached the playtime of my Dragon Age playthrough, but probably will soon).