I played with AIs for about 2 months and then I get into b-net. After a wile, like 2 weeks, I came back to Strategy AI to try the new version. Before getting online, I won every game with Strategy or Starcrack (which is a bit easier) and after that weeks of online playing I lost on Strategy and I felt that I don't have the same speed technique like before. In online playing I was focused more on strategies than skill. With AI, when you're starting to know his weaknesses, you are working to do it faster. That is what I observe in the first online faze. After 1 month of online experience, I managed to work for speed too.
Now, I found about GreenTea's new version with a lot of generals which, I consider, is the best way to improve your skill for both AIs and online playing because you're forced to scan your opponent to see whats going on.