No mad regrets, but prob stayed on 26 two bikes too long.
Bought a 26 whippet in 2011 – actually a decent bike that I liked riding, so not regretful as much as a bit of an ignorant purchase. Reckon most people appreciated 29er HT bikes were superior in that xc style at that time, just not me.
Also got a 26 enduro bike in 2012, a jekyll. This was more of a defensible buy as could you even get good 29er enduro bikes then? iirc 26ers including this actual bike won the first couple of EWS events. There was also a lot of 650B cringe muddying the discussion waters. But anyhow it was OK, plenty of good rides, just not a very enabling bike. Never felt confident with it on demanding stuff, or felt it took my riding to new places.
The complex pull shock never gave me any issues, but having two quite different switchable geometries always seemed wrong. Like if we agree that geo is important, this surely cannot be the way to design an enduro bike. But flip chips seems to be taken seriously nowadays so perhaps it was just ahead of its time.