the one i have been most impressed with is the Giant Contact switch. I’ve had Gravity droppers, a Crank brothers Kronolog, a command post and 4 reverbs (normal and Stealth)
the gravity dropper just worked and worked and worked, but was crude.
kronolog was just crap and was visibly worn before i’d ridden the bike.
Command post was a bit flaky as the mechanism jams with mud (fixed with the stealth one, but thats OE only at present)
and ALL of the reverbs i have had have failed and been replaced under warranty, some after no more than a few rides.
the Giant seems to get mediocre reviews from mags, but i think its ace. similar system to Thomson in that its a sealed cartridge doing the moving, infinite travel adjustment in its range, cable operated and a super simple seatpost that has remained smooth, best of all, it can be converted in less then 2 minutes from external routing at the post head to internal at the post base with nothing more than a multitool, same goes for serviceing. and, its £145… only downside is its only a 4″ drop, but thats more than enough!