Personally I would, its the only way of taking the strain off the UJs
People talk about wide angle propshafts which are no benefit at all when running the propshaft at the sort of angles experiences with a lift.
However your looking at £300+ for something decent.
I paid £365 for mine but it transformed it from sounding like it was going to explode to silky smoothness
You only really need to do the front one on small lifts, the length of the rear prop means that the angle that the prop is operating in on therear is less.
You can get away without running one, but you are putting lots more strain on the UJ's and if you use it everyday it "could" quickly wear them out.