It depends on how I'm running it – before this incarnation I had 160 mm QR forks with ETA on the front….if I dropped the ETA then it was fine for pretty much everything climbing wise, but with them at 160 mm it does feel a little like you would fall off the back on the really steep climbs. Certainly for the peaks though, it's been fine climbing wise.
I put pikes on it last week and took it round the Monkey at Cannock – for that kind of undulating stuff, the 140 mm upfront was great both up and down, cleaned all the switchbacks n that easily going up and was a storm going down.
With those 160 bombers on (in the pic) it's a fair bit heavier and stiffer as they are a bodged pair of coils, but, you know, I didn't really notice the weight change pedalling uphill anywhere near as much as when I changed from the light (pro-comp hubs with stans oly rims) to my heavier (pro II's on mavic 325's) wheels. I think the wheelset and tyre choice makes the biggest difference in terms of weight and climbing ease.
I do ride this bike on all day epics regularly. Mind you, I hate climbing with a passion (it's all about the downs for me!) so if your OH is a nimble XC machine and gets her kicks outta of cleaning every climb then my bike set-up probably wont suit.
In terms of harshness….I honestly cannot understand what all the fuss is about tbh. I don't have any problem with it. It's been round the peaks, ridden on DH stuff, regularly gets blatted round Malvern and I still love it.