I ride with an F7 and I have a viper S. I only got 200 miles on cause I bought it late but I can tell you my experience with it was great. When switching back and forth between the F7 i noticed the f7's rear suspension felt better. I gave the front suspension nod to my ohlins though. Speed was no comparison, on hardpack I got spanked, in powder I could pull him for a little ways then got spanked again. I get a little better gas mileage and wind protection is about the same. I like the skinnier tunnel on the cat and the height of the bars and hooks. There's no better sounding sled out there than a yamaha with a can, in my opinion, and I can listen to my sled all day long.
On a side not my friend has had his f7 for two years. He had the bolts rattle out of the recoil cover (Had to tow it back), taillight wires rub and burn out lights, thumbwarmer stop working, kept missing on top end (We never did figure out why) and now his suspension arms have wopped out the rails and he needs to replace the rails. He has around 2500 miles on it and luckily he has the extended warranty. Mostly minor issues and it's a really fun sled to ride, very agile and easy to throw around in the air. I'll stick with my viper S all I need is tripples and I could run with him if I really wanted to. Oh yeah and don't forget about the DCS it makes me a little more at ease when riding.