29erconvert
I ran an Alfine8 on a 29er Inbred for a bit, I never managed to get the chainline absolutely spot on, but I got it pretty good running a Nexus rear sprocket (no plastic cage thingy) flipped so it stuck out more, XT HT2 cranks with chainring in the middle position and an 8spd chain. I found it was VERY important to run the 8spd (or you could use a 7 or a 9) speed chain rather than an SS specific chain, as it allowed for the slightly imprecise chainline. When I ran a SRAM PC1 it kept throwing it off, despite it being only a few mm out.
As for gearing, it depends where you ride. I found the 8spd just about ok for about 95% of my riding (mine was running 34T ring and 22T cog on a 29er), only very occasionally did I long for a lower gear, and only once or twice spinning out on the road going downhill did I want any longer gearing. I did however wish that 1st and 2nd gears were closer together (big gap) and also 5th and 6th (another massive gap here), the rest of the ratios are reasonably well spaced but these two jumps are annoying. If I went Alfine again, I'd definitely spend the extra and get the 11spd myself but then closer gearing and right way round shifting are quite important to me, they may not be to you.
And yes, the Alfine does need you to lift off the pedals to allow it to downshift, but you just learn to shift gear earlier before grunting up a hill, it makes you look further up the trail (as a singlespeed would) which is better practice anyway. But otherwise, functionally, they're superb!