SC5 seems pretty good after one day of play. The online isn't GGPO good, but it's the best Namco's ever done. I was playing on a wireless router, and other than some disconnects that were probably the fault of the router, the matches were never unplayable.
It feels slightly faster than SC4, although not as fast as the first three. The super system is cool. The supers have neat properties, like Mitsus sets up all kinds of crazy tech traps, without feeling broken. Tying guard impact to super meter is interesting. As an old SC2 player that liked having GIs being really key, I don't know if I fully approve, but it's better than SC4, where the window on GI was so small that it was useless. And getting just a guaranteed launcher after a guard break is so much better than stupid critical finish. I also like the fast step, it sets up more Tekken like movement, which is nice. I don't have an opinion on just guard yet, since the online's not good enough to really let you do it.
If anyone wants to play, hit me up on PSN - PSUJer.