What did you expect, really? Why would Blizzard alienate all the fans of the first game by completely changing it up?
On the flip side, I can say that if you've played SC1 and enjoyed it, you'll probably enjoy SC2 as well. In fact, there are a bunch of little improvements (rally workers to resources, idle worker button, select more than 12 units at once, better pathing, etc.) that make 2 much less of a hassle at times than 1.