I've had 5 different rovers with air suspensions, well 6 but one was just a lease. And I have never replaced a compressor, or had any problems with the suspension - unless the control arms are considered suspension. Of the things that Mx mentioned, I've only had one case of water through the cowl and one case of EPB blues.
I've definitely had more problems with the older RR's. I tend to think of them as being more akin to discovery 2s as their underpinnings are more similar. Had a tranny go at 60,000 miles, had a top end job done at 70,000 miles, had a $1000 heater core O-Ring replaced. So I think they are simpler in terms of electronics but none of those things had any business breaking, and were all terribly expensive. I spent more on the top engine rebuild alone than I spent on my LR3 in 8 years of ownership. All that said, I really like older disco's a ton. They are the last really true old school trucks of the lineup to make it to the U.S. Can't help it, I still love solid axles!
Is it more expensive and fragile than a 'toyota' GX? Sure. But if most of the first 100,000 miles problems have been fixed, than you should be able to sail up to the Gx's 140,000 miles pretty cheaply. If spending 30-50% (est?) more to fix it is an absolutely huge concern, then maybe the LR isn't the right choice.