Default A few questions about getting this phone unlocked

First off I am on my dads cell phone plan and am not paying anything a month for it so I dont want to switch to t mobile but the att version has a locked bootloader so here I am. So for my first question, how hard is it to unlock one of these phones? Then once its unlocked, will it get worse service then the att version? Can this unlocked phone tether like the way a stock t mobile one can? Is there any other down side to getting an unlocked phone vs stock att other then the unlocked would have tmobile on it instead of att and root access right way. thanks for any help and if I posted this in the wrong thread, im sorry.