I used to have a 2.slow, and to be fair it wasn't as bad as people make out. It was a nice, smooth car to drive, and when compared with a 1.8 20V NA late one night, there was nothing in it. Fuel consumption was around high 30's too.
I looked at changing it for a 1.8T when it was a couple of years old, and to be honest, was really dissapointed with it. I expected it to be lots faster, but the reality was, it wasn't. I ended up buying a Leon Cupra.
The downside of the NA engines, is that you will never get any noticable power gains from them, so you are pretty much stuck with what you buy, whereas a 1.8T or 1.9TDI is just a remap and exhaust away from an extra 40bhp.