Another disadvantage is repairability. If your chain snaps you can fix it with a quick link or a pin and a little multitool with chain tool functionality. If your belt snaps you‘re screwed, unless you carry a spare belt everywhere.
Here‘s a (German) Video from a guy with a severely damaged (but still rideable) belt after 4500 km:
https://m.youtube.com/watch?v=n16gN7RDWEY
In the comments you‘ll find people whose belts snapped at 1050 km, at 1000 km and one at less than 2000 km.
I don‘t know how likely this is, it might be quite rare. But since it‘s non-repairable it‘d make me uneasy on longer bike rides.
Belt damage? They put these belts on motorcycles, it's possible to damage them but they are insanely durable, probably stronger than your typical chain. Somewhere I picked up a staple on mine, I'm going to get it replaced but I've done several hundred miles on it with no issues.
The IGHs are a different matter, they're pretty sensitive and if you get them off a little bit they work but your shifting will be hosed up. Bike shop fixed it all though. My advice? Don't mess with it, get it set up, make sure the little connector on the cable is tightly attached and you probably won't have issues, I had some slip on mine.
I've been running Conti touring tires with some mixed tread and pre-slimed tubes, I've not had flats but I've worn out 3 or 4 sets of tires. It's not a big deal to change it though. It's a commuter bike so it has bolts rather than quick release skewers, I'd use slime and maybe even kevlar liners if you get a lot of flats and just make tire changes a wear issue. It's a heavy bike, it's not a carbon roady by any stretch but it has been as close to zero maintenance as any bike I've had. It's actually required more maintenance on the disc brakes than the drive train, they were getting a little squishy but just rebleed them and they're good again. The only "issue" I've had was when I got a lot of dust on the belt, it was kind of squeaky for a while.
This carbon/ceramic drive shaft is kind of interesting. I always thought that the chain to pully and gear touch point was where the friction loss was, not interlink on the chain itself. For years and years, they've offered bigger pullies for reduced friction. This drive shaft will still have a similar touch point; also seeing as how both pieces rotate, it looks like there could be side to side friction as the cog on the shaft touches the gear on the wheel and they both rotate unless the cog and gear have some very special shaping that I'm not seeing. As the cog rotates, when it first can engage the gear, just the tip will be touching the gear but as it continues it will push more of the tooth on the cog in to the gear, am I wrong on this?
For what it is, I love it, it's not a racing bike though. I'm curious about the mtb uses with a Rohloff hub, it's a fair amount of weight.
[1] https://www.hebie.de/en/protection/chainguard/chainglider/35... ?
Are bicyles a fashion statement, or what?
"Seht her wie geil mein Riemen ist!"
Mine also has the Alfine 8 speed hub, which is kind of suck, but I make it work. I recently had it re-lubed (dunked) at my LBS, which seemed to help. I just wish there were some nice IGH in between the Alfine 8/11 and a Rohloff. I'd gladly pay for something better than the Shimano.
For commuters, I cannot fathom why people would deal with a chain when belts are a thing. Plus, good chains aren't cheap (I like Wippermann) and when you rack up miles you need to replace them enough that your wallet notices.
Tires: +1 for Schwalbe Marathons. Four years and no flats. NB: if you are worried about weight, upgrade to the Marathon Supremes with the aramid (foldable) bead. ~$75USD/each but totally worth it.
Oh yeah: a dynamo hub is a life-changer. My Focus came with a SP PD8 and lights, stock. Never having to strap on a light, or remember to charge it is a revelation.
Ride safe!