Go for it! post a WTB ad on Craig's list or check out your local bike coop to see if you can get some cheap to try out and if you love them go ahead and buy some nicer ones.

Also, and I know it's not what you asked, but you could switch to drop bars for pretty cheap if you didn't want brifters. Good bar-end shifters and brake levers can be had for very cheap. Downtube shifters are even cheaper.