On the opposite end of things, I like a manual shuttle for most everything. Most, 'cuz I have a PTO stump grinder that uses the tractor motion to drag it across stumps. That is tedious with a clutch! So I usually "roll the bucket" to pull the tractor forward (unless the stump is on a slope, for which I just ride the brake.) But that's the one and only thing, so far, in 150 hours of "tractoring" with shuttle, and I may make a one-wheel driver to go on the SSQA mount to pull it along, if I find I'm using it more than I thought.
In the last couple of weeks I've moved about 30 yards of topsoil, and 20 tons of sand and gravel, using the FEL. I don't even think about the clutch, and shifting the shuttle, I just do it! No problem. Also, it's nice to, say, drag a sub-soiler without doing anything but steering. More power at the PTO for a given engine, as well. I've used a box scraper and a finish mower, no complexities whatever.
I'd imagine that I can fix anything that goes wrong with my manual transmission (but it's likely that nothing will go wrong). I don't know about an HST, certainly it would be more costly.
And it's cheaper with a shuttle—you can spend less money on a tractor, or get more tractor for the money. Finally, you can build up your left leg muscles! (Actually, I did feel it a little after a day's dirt moving, but got used to it quickly.)