like everything in life you get different types, the stuff these guys sell is good.
http://www.yolo.co.uk/heat-transfer-paper-1-c.asp
the thick stuff for darks cracks, the thin stuff for lights is soft and has a good feel. you definitely need to trim or you see the transfer itself, and its also worth playing with your print settings to get the best print results.
it will work with an iron but a heat press is best.
hugely though with printing it depends what you want and how many. for what most people pay for a blank T it does’nt take many shirts to get to a point where someone with some kit could do you run for the same cash, maybe not screenprint but definitely transfer or vinyl. well i could anyway but then i’m cheap!