Strengths: Makes a hard tails like a susser, increases traction on technical climbs.
Weaknesses: Price/weight
Overall: I got this because I had become used to my sussers and found the hardtail horrible to ride, this clever piece of kit changed all of that. DONT waist money on silly telescopic MTB versions (been there) and spend the extra few quid and you will not be disappointed!. You can adjust the threshold at which it becomes active and also adjust rebound and compression (elastomers included), i am very pleased so far and would recommend this to anyone.
If you want to really finish this fantastic piece of kit off get a crudbuster cover to protect you pivots from muck and uneccessary wear.
Weaknesses: Crappy travel adjustment that messes with pivot points hence causes set up problems, every time you change the travel you need to re set sag, even then the bike feels strange.