Well we brought it yesterday, and yesterday alone clocked up ... just over 7 hours each (playing co-op the whole time), as yet to get a multi-player gem and some bits don't quite make sense yet, but what a blast !! Both melleeing can be a pain if you are close and sometimes you can block your friend arrows, but the flail used right is amazing, pull your friend out of trouble, get them to drag you where they just went.
We're both using wisp as our companion at the mo with her spells upgraded to level 2 with a gem so can both heal 60 a time, the rage/fury reels are brilliant fun and money was tight until by pure luck for the first time we both rolled jackpot at the same time and got lots (and quickly spent it all merging gems and getting better armour and equipment)
I can't say about single player but co-op it's a HUGE blast, will have a quick go today though fixing someone's PC later and then dinner out so not as much as we'd like.
P.S DS-Lite cramp hurts after playing for 7 hours