I've used almost all of mine so far and haven't had an issue. Setting it up can be a pain in the ass, but once that's done, there is little to do other than verify your attendance every month.
You would be best off talking to the VA Certification official at the school you plan on attending, they can get you setup and answer all your questions. There is a few different GI Bill programs out there now, so make sure you pick the one that best suits your needs as far as money and housing costs, etc. (pretty much, pick the one that will make you the most money)
Explore this site:
http://www.gibill.va.gov/apply-for-benefits/
it has almost any info you could need, anything this site cannot tell you, or you don't fully understand, your schools VA certifying official should be able to answer.
Good luck.