In a word: flawless. I can’t really find anything functionally wrong with it.
Just like the 125mm version, the 100mm Reverb has zero play both extended and compressed, so there’s no annoying saddle rocking or creaking noises. Push the remote, give the saddle a quick butt-tap and the post drops right down. Push it again and it pops back up, at a rate controlled by twisting a dial on the remote.
The 100mm option is a bit shorter than I like on a trail bike, but is perfect for a less aggressive rig or rider.
The only two downsides are weight —538g for this 355mm long version, heavier for a longer post — and where to run the remote line if your bike isn’t set up for it. Creative zip-tie work is really your only option, and that can be a bit unsightly. Just cover it all in mud and nobody will ever know.
Even so, I’m planning on running this shorter 100mm version on my full suspension XC rig next year, and the 125 is on every trail bike I ride. The time gained on the long descents here in Colorado is worth half a pound on the climbs for me.