Just to clear up a few superstitions, here because I recently picked up Viper online as a secondary to my Abel.
As alot of people here have said, online and offline are two completely different creatures, with the same coat, color, eye shade, attributes, style, and scent. To be perfectly honest, the biggest difference is really the level of what you’re facing both on and offline, and the ability to put on a good show. (Aka Get away with more crap)
Linking is really difficult online, there is a chance you’ll be able to do what you have intended but odds are you won’t. Odds are you’ll also be fighting Ryu, Ken, Akuma, Sagat primarily, and Chun, Guile, Rufus, and Rog as you move up the ladders.
G3 - Enjoy the J.HK > c. Hk Ken, he loves that move.
G2 - Enjoy the J.Hk > c. Hk Ken, he loves that move. But he might throw you. Blanka might make an appearance.
G1 - Not terrible, not all that bad. Might meet some turtles, but you can win.
SG - I wouldn’t know.
I wouldn’t consider myself good enough to take C.Viper outside of a few good connections G2 games with my ass still connected, but just using her and her high flying, high speed, stylish combos for a few hundred online matches I can tell you most importantly.
Keep it simple.
Know the character, play the player.
If you can punish it, then punsh it.
You will lose, alot. Alot of times to bullshit, but everytime you lose or even get hit, you did something wrong so learn from it regardless.
Online players are typically more aggressive then the guy next to you in the arcade, keep this in mind.
If you lose to something, or have thrown your way out of a round to one move, just focus on beating it.
[*] Understand your connection, try to get it out of the way very quickly. Once you know what you can do in a fight, your options open up. I try to start with light attacks till I know what I can do against my opponent, then open it up.
I will not lie, that playing with complex characters like Fei Long, and Cammy which require alot of timing and practice to excell with is frustrating and usually not worth the effort, but to those who still do they’ve made a decent mark on the SF4 community.
Like I said, just keep it simple and play to play, play to win, or play to learn. Usually you’ll get a few portions of each, everytime you power up the game. If you don’t take yourself too seriously, and can stomach seeing Ryu every ten seconds, then I guarantee you’ll do fine in online.
Viper in particular just has a bit of jet lag.