They are great off road, and were far better than the Land Rovers that replaced them. M O D were cost cutting even then.
Main problems could be parts, they aren't cheap, and if you are fortunate enough to find one with the RR engine, rather than the one built under licence by Austin, seals etc would be a pig to locate.
It's also worth noteing that they can make a Range Rover look frugal when it comes to fuel consumption.
Has the one you have been offered benn converted to unleaded fuel? If yes, make sure that it's a genuine conversion. People have been known to lie to make a sale. The only one I know of on the road local to me, hasn't, owner has to travel to Swillington to buy four star, and it isn't cheap.
All in all a great motor, but not one that you would want to break too often, running costs of the genuine article will be high.
Pete.