They are a truck you either love or hate and with plenty of quirks. They are best suited to the true enthusiast rather than someone who likes its rugged good looks.
I've had one for 10 years and still love it. I find it handles better than my series IIa 88 (Both trucks are well looked after), brakes well enough to get the back wheels of the ground if I want to (The front brakes are the same as a late series 109 and the rears are almost as big to match the 1 tonne rating. At 37ft the turning circle is tighter than a 109 and IIRC better than an 88.
It was never intended as a rock crawler and has the same issue as a lot of military vehicles as the suspension was designed to operate with the vehicle loaded. Add 3/4 tonne of gear and the suspension moves just fine - travel will always be limited by the spring length, short shocks and short shackles but actual wheel travel works out about the same as a stock series.
Some, but certainly not all, of the quirks you will have to deal with are the unatural position and throw of the gear stick, the infamous prop shaft rumble, a fairly cramped driving position and rear visibility. Ride suffers for the usual FC reason of the driver being directly above the front wheels but the view off road is great. Military bar grip tyres are 'interesting' in anything other than dry conditions. Given its airportable nature where everything strips off the truck the roll protection on a GS is marginal.
65mph is about all you want to do with either an overdrive or regeared TC. They can do more but it goes from the merely painful to really questioning your sanity. As it a low compression Rover V8 powerplant power upgrades are easy and the LT95 gearbox will take all the grunt a Rover lump can throw at it.
There was never a great number of them built in the first place and they have been out of service for a few years now so finding a good unmolested one is quite difficult.
There is a very active club with parts support at:
101 Club
As you may gather I fall on the enthusiast side of the fence.