Oh man :/ I want somebody to play with on PC.
Browse the huge SF4 thread on GAF; plenty of PC players on there. Or better yet, go to Shoryuken.com.
I'm not very good at SF4 and I'm not at all sure how to get any better. At this point, do I just have to sit in training mode and keep trying to get the same damn combos down to near muscle reflex?
I keep playing Arcade and other people and I'm never any better than I was.
Just keep playing online matches. Training mode helps to get down combos, yes, but it's being able to execute everything during fights and also just learning match-ups that will help you to get better. Hit up Shoryuken.com and check the forums for the character or characters you use. There are some very helpful tips on there.
You're not gonna get any better without playing people online. Playing with a friend who is better than you is especially helpful because they'll give you tips while you're playing and point out your problems.
Yes, DEFINITELY this. My game got way better just because I have been able to play dudes like FindMyFarms on PSN who is way too good at the game. He always beats my ass, but it's really helped me to pick up on stuff. I played an awesome Rufus player who also showed me ways to take him out using Chun-Li.
You're not gonna get any better without playing people online. Playing with a friend who is better than you is especially helpful because they'll give you tips while you're playing and point out your problems.
Yeah the one friend I have who beats me just mocks me and laughs every time he wins, and he doesn't know much about the game anyways, he's just using an arcade stick and got really good with it.
Okay, so who do you use and who does he use? Definitely hit up SRK for strategies and also be on the lookout for stuff he does and stuff he tends to fuck up on. You can often bait people into doing one thing and totally punish them for it. There's a friend of mine who has a huge history of shit-talking; his antics have even gotten him banned from other forums. He proclaimed himself a better player than DAIGO and said he could take him after watching some EVO videos.

Of course he wanted to challenge me, and I shut his ass up over three mini "tournaments," with the final outcome being 51-17. And those 17 losses? It's from when I didn't use Chun-Li and went with random select or Dan.