If you do much freeway driving, you do NOT want a 16 tooth front sprocket on the 550. I certainly didn't like it. But, it did help with the stop light grand prix in the city. 
The 16T only helps in first gear, IMO. Otherwise, if you need better pick up, drop a gear to get it.
Cheers,
+1 to that! I live in the north metro georgia area which is VERY hilly at times but alot of straight ahead hwy as well. My bike is huffing some rpms to keep 65 so I went with the 34 in the rear to get some better top end. Yes you'll lose some take-off but you also won't be searching for 6th gear once you hit the hwy.
It's all a matter of personal opinion and feel. For me, if I were doing mostly highway riding on my 550 I would probably stick with stock gearing. As it is now, though, I do about half highway/city, and I find the 16/37 to be a good compromise for both. I'm willing to increase the 5th gear rpm a little to achieve better acceleration in 1st gear. Others may not be. Going the other direction in gearing will decrease the 5th gear rpm, but it won't increase the bike's top speed.
