Gotta watch the intake boots on all Polaris sleds. My 08 700 burned down because of the boots. Warranty covered it. I have 6800 hard miles on mine now. Motor was done at 2400 miles, replaced 1 idler wheel bearing at 5200 miles. That is all I have had to fix on my sled. I redid the clutching. Before it was slow, same speed as my brothers 600. Now I outrun 150hp class sleds up to 100mph. I have never did a top speed run, but I have hit 107mph. BTW mine is a 121" track. With a little fine tuning, the 700s are very fast sleds. Mine gets anywhere from 10-13mpg depending on how I drive. It uses a good amount of oil, but it is adjustable, but I use the cheap Polaris oil and dont really care about oil consumption.
Good motors, but you gotta check the intake boots often. I dont have any experience with the 136" track or suspension.
The reason why Polaris dropped the 700 is because the 600s are so strong, and they came out with the 800s, there wasnt really a need for the 700 anymore.
Oh one last thing, gotta seal up the headlight and airbox, all IQ chassis sleds sucked in ALOT of snow dust. Easy fix, takes 20 mins. and $5.