Metz ME880's and Shinko T230 are probably the two most popular tires here.
Metz:
+Good tread life (relatively, depends a lot on how hard your ride)
+Very good "feel" and handling
+ Top quality tire
- Expensive. Rear is ~$150, front $120.
Shinko:
+Super grippy, if you want to wheelie these are for you
+Cheap, a tad bit more than half the price of the Metz.
- Don't last very long, have heard several reports of less than 5k miles.
- Often take tons of weight to balance (quality is spotty)
Your stock rear is a 150/90-15. Many people put a 170/80-15 on instead, which will fit in the stock swingarm with no modifications. I've found the Metz is actually cheaper in 170 than 150, so go figure. You can put a 120 in the front also, but it'll mess with your speedometer. I found with a brand new Metz 110, my speedo was almost dead-nuts accurate run against a GPS, and as the tire wears it starts to be a bit "optimistic".