they have little traction in serious mud we had them on a construction sight and spent more time pulling them out of the mud than riding them after a big rain.
Proper tires make all the difference on any ATV, especially in mud. The stock tires shown above, usually Dunlops, are not-so-fondly referred to as "bologna skins." They are worse than useless in the mud, so unless you are planning to bug-out around the back yard you should replace them on any new wheeler ASAP. Quality all-terrain or dedicated mud tires like Dirt Devils, Sur Traks, Mud Lites, or Titan 589's are available for $200-$400 for the set, and will turn any decent sized 4WD ATV into a mudding machine. It's the very first accessory I buy for any new quad.
As far as your other points go it really depends on what the situation is. I ride a Yamaha 400 Kodiak. My top speed is 52 MPH and my buddies newer, bigger bikes are considerably faster than that. The on-board 4 gallon gas tank will take me about 85 miles and if necessary I can easily carry 4 more gallons on the rack--not to mention what I can tow. While nowhere near as good as my truck I can forsee situations where bugging out in my truck--or any car for that matter--will not be possible. Then, as you say, I'll be mighty glad to be riding rather than walking.
The next ATV I buy will be a
Yamaha Rhino 660 , which is similar to the one pictured. We have several in our circle of hunting buddies and they go everywhere the regular ATV's go, and a lot more comfortably to boot.