Hi i too was in the same dilemma as you at the end of last year, as i was riding a 250sy and have done since they first came out. I wanted a new bike but weren't sure if to get another 2 stroke or a 4 stroke, after thinking long and hard about it i went for the 4 stroke and jumped into the unkown.
Now i have it i feel i have made the right choice i have had it 4 months now and not really had any problems at all, i had to change the main jet and lift the needle one notch but thats it if you can call it a problem.