i guess there are 2 things here :

1. having accent is ok as far as you can make others understand your point in english ... 2. bad english (i mean really bad) will be turn-off anyway with or without accent .... so it is not accent but its all about english as a language i guess ...

I've seen people with english and no bad accent but still having trouble in making other people understand :) and they are either Dumb OR they're P.hd holders (not generalizing though)...