Naturally shaft drives need to be maintained, but it is not a big deal and far less often than a chain.
Yes they limit the tyre size at the back in general- but a modern shaft BMW has wide back rubber.
The rise and fall issue is not a big deal once you get used to it. Modern Guzzi and BMW bikes have a parrallegram rear end which stops this been a issue.
Weight wise, the BMW system is actually pretty light these days.
The only chain I have ever seen last the life of a bike is one on either a postie or crashed before its time was up. The chain on a modern bike takes a huge amount of power and if used as designed, does not last. Sure a slowly ridden one will last a while on a superbike.
None of my mates have ever got past 70,000 k on a set with religious maintenance.