between just getting your chain the right length and maybe a half link, chain tension shouldnt be a big deal. ive had coaster break set ups before (i used one instead of fixed for a while when i had a broken arm and didnt want to skid one handed), i foudn them to be a pretty big pain in the ass (all the blah of singlespeed, and still had to lift the seet to get the pedal in the right spot when I. id rather get a singlespeed set up, or a freecoaster for goofing off on...

right now im quite intrigued by 3speed rear hubs. but thats just me.