Well I had an 08 5.5 here’s my thoughts; Not the lightest as pointed out and the paintwork was of a disappointing quality, the back end did seem flexy at rest, I eventually cracked it.
BUT it really was a great bike! The contact system suspension is truly excellent for tracking round corners without having to scrub speed, the bike just made you go faster downhill. Despite weight issue it was by no means a slouch on the climbs and propedal on the RP23 masde things a bit easier. But probably because of hammering it so much I ended up with small crack at head/top/down weld. I decided a bigger bike was in order and had no bother getting an 08 666 as a warranty replacement. And I **** love it.
Don’t think you’d be disappointed with a 5.5, they are excellent, fun, enagaging bikes. Even if they are too “Trail Centre-ish” for some of the bike snobs on here?
Btw no real comparison to a Zesty, tried one of them of my mates for couple of weeks and this seemed altogether more lighweight, racery type. Descent handling especially was decidely twitchy compared to the 5.5. IMO of course!