I wouldn't call the learning curve "huge", but there's definitely some thought that has to go into every round of combat. Once you get it down though, a fight can be resolved in minutes. The hit tables are one of the best features, I think, but they definitely do take getting used to.
The magic system is not my favorite, but I do love the epic feel of it. For my campaign we're using an Ars Magica conversion, but they'll be having a supplement come out in a few months that offers an alternate core magic system, which I will definitely be buying.
Riddle of Steel won't replace D&D on your table, I imagine, but it'll earn its own place in the gaming spotlight.
The quickstart rules are a good introduction. They don't capture all the flavor, and certainly only half the excitement of the amazing full system combat rules, but they'll give you a fine preview of it.