I'll tell you the biggest beefs from owners.
(too low of ground clearence)
(very weak frame- $400 investment in metal skidplates a must)
(viscolock- slow to engage in 4 wheel drive when you need it. 3-10 second delay, supposedly fixed on the 09 models according to their advertisments)
(heat issues as in getting hot leg and melting plastic)
The 800 is the fastest stock atv until the 950 Thundercat (arctic cat hits the dealerships)
Overall great machines from what I read from owners. one other negative I'm not sure of is that you have to bring them in for a lot of hourly services at $200 a whack. 10, 20 hrs etc. Maybe someone else can confrim this. I read one guy complaining about this.
I own a 800 XT and have used it for fun and harvesting a caribou and a moose this year.
There is low ground clearance up front stock, I get 10" instead of the advertised 12" and the front springs are not as stiff as they should be. This can be remedied by taking the quad in and complaining, and calling BRP. They will either put the two seat springs on the front or thier HD models ($67 to buy out right).
The frame isn't weak, but the front part is subject to damage/take the brunt of the dammage with the light springs on it. But as with any quad it needs skid plates, even my old Honda needed them.
Visco lock, not much experience with it but when it engages it engages abruptly. Havn't got the quad stuck often enough to really need it but when I did the other 3 tires had dug in pretty good.
Heat, yes it kicks out some heat on the side but nothing unbearable. I think all the big bore quads are kicking some heat out. I havn't melted any plastic on mine and I have many miles of really slow speed riding as well as high speed.
As for taking it in for service its like a new car, they reccomend that you take it in for all the sched maint as well. The only one you HAVE to take it in for is the 10 hour so they can take the limit off the ECU. Other than that, do your own maint and keep the records. There is the 10 hour then like every 100 hours after that. I plan to take mine in for every other 100 hour (probably anually).
Many complain about the price but once you buy almost any big bore bike and equip it with racks (front and rear), hand gaurds, upgraded 6 ply tires and rims, and warn winch (all dealer installed) then you will find that the price is quite comperable. But this one comes with a 3 year warranty.
Now for the opinion, my first ride I came back from with my elbows and shoulders hurting from holding on. My face hurt from the grin from ear to ear, and the seat cover had one big pucker mark in the middle of it. I havn't had the huevos to peg the throttle yet but I have raced traffic on the hiway at 65 mpg with plenty left. The ride is out of this world, super comfortable, super stable definatly makes it worth it.
Personally, I think if you drive one you will have a hard time considering anything else. Oh, and with these you need to get one motor size smaller than any other quad you want to compair it to because they have more HP and TQ per cc. As for the thundercat beating it, the pre production cat is faster on the big end after 600 feet but I want to see what the production bike puts out (just like the king quad in 05, they had to reflash the ecu to take power out). Not to mention it is taking a 950 cc quad to barely beat a 800 cc quad.
Rode the two up 800. You do have to hold on. I was able to go places in two wheel drive the others on 650's were going in four. Of course the 27" Dirt Devils helped. Amazing ride, very fast, but controlable. It will get away from you in a heartbeat if you don't respect it's acceleration. I am probably hopelessly spoiled now as I haven't ridden any other big bore. The ATV's that I rode are owned by two guys that do not baby them by any means and they are taking the abuse well. Wonderful machines and I would own one in a heartbeat if I could afford two (one for the wife). I can't see how you could go wrong if you can afford it. As for the Thundercat I can't see why I would want to go faster than the 800 Outlander and I like to go fast. Great suspension by the way. You can flat out fly through whoops even with a passenger.
Consider going to the 400/500 XT. I have an 05 Outty 4x4 XT and love the heck out of it. My upgrades have been racks, air filter, synthetic fluids, Mudlights, Elka front springs and grip/thumb warmers (in addition to the usual front/rear/fender bags.
As most of my riding is done under 20mph I didn't find it necessary to get one of the monster machines. Not that I wouldn't love to throw a leg over one, I just get most of what I want done with the 400XT. It sips gas, goes most anywhere I want to go and has a recoil backup starter that has saved my butt twice now (due to my own inexperience). This is a very nimble machine that is even better now that I have the stiffer front end--no more body roll. Yes, I'd love to have more ground clearance but I'm willing to live with what i have presently. As aforementioned this machine will run just fine with the 500cc machines and I'm pulling 57-59mph on oversized wheels.
I love mine enough, in fact, that I've even purchased extra camo fenders, footwells and covers. It is my plan to keep this thing around for a LONG time unless someone offers me a silly amount of money for it (feel free to do so).
As for maintenance I've gone in for scheduled visits while under warranty and then had the CVT belt and front brakes replaced at 1800miles with 20% wear left over. I'll replace the spark plug this year, too, but little else is required on these machines.