Okay, so you've heard from the biased carrier owners, now you can hear from one who doesn't own a carrier.
Cons:
You can't just hop in and take it for a ride, not street legal, so you're limited as to where you can drive it
You have to trailer it pretty much everywhere you go. Unless you get a special permit for road use, you're stuck with a trailer. So add the cost of a pickup and trailer to any cost of a carrier, unless you have several acres to play wtih.
If you're taller/bigger good luck driving it easily. Sure taller drivers fit, but it's not as easy as the little guys who just hop right in.
Parts are harder to find than other MVs, but not impossible. This forum is a great place to find them.
Pros:
As was pointed out, they're a pretty small vehicle, so pretty much the only fully tracked armour that will fit in a regular residential garage, and that you can easily transport with a truck and trailer
Come on, it's a universal carrier! They have that functional ugliness that is so beautiful to all British MVs
Depending on where you live, they aren't that common. There are a ton in S. Ontario, but when you go from there, they get rarer and rarer.
As was pointed out, there is NOTHING like a ride in a carrier, cruising across a field with the tracks slapping against the fenders, and every bump passing smoothy underneath.
All in all, if you have the room to drive it, and a vehicle to pull it I don't think there are many other vehicles that I'd reccomend. *I* personally would never own one, but then again I have two or three friends who already do, and who don't mind sharing
Tim