Here's my take, based on 25 years (my god has it been that long) of dealing with Blue Oval Muscle...it's not so much just the rear wheel drive--though Front Wheel Drive is much much better in "foul" conditions...
First: Mustangs, particularly GT's and Shelby's, have a lot of torque heading to those rear wheels and that's what causes some of the "tail happiness" to occur--of course, guys with heavy right feet (like me

) like that sort of thing. I don't know about the V6's so much as I've never driven one, except as a rental, and it was in nice conditions. Traction control helps some, so does the digital throttle response unit, but from what I understand rain snow and ice are still "exciting" in the new body style.
Second: Long nose, short deck Pony style "muscle" cars are NOTORIOUSLY nose heavy, butt light---which makes for less than ideal traction at the rear wheels in poor conditions--add the power of a Mustang V8 and you have recipe for excitement

, as well as rockin' burnouts. Good if you're an idiot sliding the rear end out and having fun (like me

), bad if you're transporting the kids to the mall in rainy weather.
The newer models are GREATLY improved over the old models, and an automatic "handles" handles better than a straight drive. Overall, by design Mustangs are light in the rear, though again, Traction Control has helped tremendously. They also like to understeer, but unless you're really pushing the car, you're never gonna' experience that.
I drove a 93 LX Notchback 5.0 as a Patrol Car when I was a cop....man I had a blast in that thing, but there were times (rain and snow) I had to drive very very very carefully---it was a 5 speed and it would break out on me real quick like. Matter of fact, I had one officer who jumped in with me going to an "officer needs assistance" call refuse to get back in the car with me

. Said she'd never ride with me in "that car" again

On my hot rod Stang, I moved the battery to the rear compartment, and this helped some, but not a lot. I had to be pretty careful behind the wheel.
Edited to add:
I wouldn't hesitate to buy a new one. They are much better "commuter cars" than the older models, especially the V6's.