I have a 2010 Ranger 800XP side by side, with a bunch of options on it including a full Ranger Ware fiberglass cab, extreme bumpers front and rear, Warn winch, A-Arm guards, oversized tires and spoke aluminum wheels, etc. I've also made an aluminum rack that fits into the holes in the top bed rails so that I can mount my 10 1/2' Titan fly rod/reel carrier on top, and have a custom made enclosed/lockable poly box in the bed to carry some of my fishing gear.
Mine has been a pretty good machine overall. I keep it in MT, where it is legal to drive them on the highway (although I only go a short distances), it has been reliable so far, and (generally) gets me where I want to go, and back home again.
Here's the negatives, from my limited perspective: They are expensive - mine was $20,000 or so fully equipped, plus I put another $4,000 in a trailer, and also had Montana Canvas make a custom cover for it. They are somewhat hard to service, if you are planning to do your own routine maintenance - fluid check points, and drain plugs are hard to get at and require some special tools (at least for mine), and I understand the older ones were even more difficult. Because they are belt driven, mine doesn't seem to have the torque that I wish it did, and I've been unable to drive it into places that I'd have wished I could access - however, on the plus side, I am able to get into and out of some pretty tight spots to launch my 16' drift boat (about 600-700# including its trailer). Probably the most dissatisfied thing about mine is the Ranger Ware fiberglass cab. The quality of that thing it pretty bad, and I wish in hindsight I'd have never bought it, and would never buy another one again.