It seems to be very popular on MTB's in the US, certainly no shortage of reviews. The top 3 hubs gears are Rohloff, SRAM I-9 and Alfine, I think we all know the Rohloff is in a class of its own, but so is the price

Of the other two I went for the I-9, but it was a close call, better shifting and trigger shifting option make the Alfine attractive. Extra gear and better gear steps make the I-9 attractive. The kicker for me was ease of wheel removal, I went I-9 because it has an easy release and SRAM have a better reliability reputation than Shimano, in hub gears. The amount of 'how to' videos on the net re Alfine wheel removal/installation is an indication of how big a pain it can be. But a few practice runs and it apparently becomes quite straight forward.
After running the I-9 for a while I'm not sure I wouldn't go for an Alfine now

I've been very unlucky in having the I-9 seize on me but you really feel the lack of stockists and repair options, in the UK, when this happens. I don't like twist shifters, the main benefit is the ability to change multiple gears in one twist, I can't think of a time I've used this facility. The I-9 is very heavy, probably 1kg more than the Alfine and 0.5kg more than the Rohloff. Riding style matters as well, I tend to rid SS with gears as backup, ie only changing when I really need to. The Alfine gear range would be fine for that style. Running a 20/40 combo gives you 28 to 88 gear inches. This is commuting/ light trail stuff, if you want more serious offroad then you'd need to sacrifice at the top end.
I genuinely don't understand why Shimano don't have an easier release mech for wheel removal. Fix that and I'd definitely have an Alfine.