I got my first fixed gear a couple of months ago. I would say that if you are not going to ride track, you should just find an old steel road frame on craigslist. Make sure that it has horizontal dropouts so you can adjust the chain tension. You can replace the wheelset or even just the back wheel with something nice from your lbs, iro, ebay, etc. Then take off all the stuff you don't need, like derailleurs, back brake, unused chainwheels. It's a fun project and it's not that hard even for someone as IQ challenged as myself. Just a warning though...the back wheel alone will cost quite a bit when you account for the wheel, cog, lockring and freewheel on the other side if you're going to run a flip flop. And to answer your question about the flip flop, you'll need a wrench to take the wheel off. Also, if you're going to run different speeds on each side, you have to get the chain length just right. When I first converted, I had a 13t fixed cog on one side and a 16t freewheel on the other. When I had the 13t spinning, the wheel went all the way back into the droput and when I had the 16t freewheel, the wheel sat pretty close to the front. You'll have to play with this on your bike if you run different sized cogs.

If you go with the conversion and you play your cards right, you'll be able to do it for less than the Pista you are looking at. However, if you just want to get into fixed as fast as possible, the Pista for $400 doesn't seem like a bad deal. Personally, I've never ridin a track bike. The geometry is different than a road bike and from what I understand will have you riding in a more aggressive posture. After all, it's made to race on a track! Good luck!