I have an '03 636, great bike.

The seat is terrible, it's gonna crush your balls, I reccomend getting a shaved seat to flatten it out a bit. The tach is also kinda of a pain, it's LCD and kinda hard to read at times when you can't sit an really look hard at it. And the valves tick on them nothing to worry about though, just scary if you don't know whats up.

Other than that I love mine, handles great, very tossable in a turn, light, doesn't stretch you out too much, but when you tuck your knees kind of get in the way. Lots of power for a 600. I suggest you get an exhaust either full or slip on, and a PC III to really bring it to life.

The '03/'04 636's were in the top ten greatest bikes of all time, and can't find the article right now, but rest assured there great bikes.

Hope this helps