How much of a factor does latency play in SC? Being from EU but playing on NA, will it affect me in any way?

Well, switching from EU to NA will definitely affect you as you'll probably be loosing a lot more games than on na. Dont get discouraged tho, by playing better people you get better.

I'm still getting into the game, though. Still deciding which server should I invest more into, that's why I'm a bit skeptical on the latency issue.

Its not so bad. You will hardly feel it, there may be 0,2 seconds delay from your click to when it actually happens on the screen. It's really noy as bad as jerhyn says.

This, definitely worth playing on NA just for the skill increase

agree NA > kr