My thoughts on this:

It's equipment that works, but it's not the panacea that it's sometimes billed as. Here's my experience with the Alfine 8:

You will immediately notice the extra weight, and the drag. It is noticeably heavy and draggy, with a great deal of weight concentrated in one very dense location, but some might consider that the price to pay for extra reliability and weather-proof performance.

However, it was not reliable at all for me right away. 5th gear would slip, the pedals spinning more-or-less freely without driving the bike, all while the hub made horrid grinding noises. Then it would re-engage, only to slip again. 5th gear is the one where the roller-clutch transitions between over and under-drive, and that gear skipped like crazy, particularly under effort. I should point out that my maximum effort is the effort generated by a 135lb cyclist who is, at best, Cat 5 pack-fodder just hanging on. I don't abuse equipment with weight and/or power. Within the course of just over a year, I paid two different shops $100 each to look at this, and after they assured me it was fixed...it wasn't.

Warranty, you say? All of those shops were Shimano warranty centers, and they wouldn't warranty it. Claimed the setup was bad, or I had the wrong kind of cable ferrule, or it just needed overhauled and serviced...and they were both glad to charge me.

Eventually I sorted it on my own. I have started to scoff whenever the stock answer on BF is "take it to your LBS". Two shops, and more money in maintenance than I spent on the car last year, with very few miles on that hub to show for it. I have yet to find an LBS that can fix my bikes better than I can, and after a lot of reading, I got this as close as it's going to get.

The skipping is mostly gone, and I've been riding it around now mostly trouble free for six months. I've found that the system is EXQUISITELY sensitive to cable tension/position, and swings in temperature will alter things to the point where I need to readjust, because 5th gear will grind again. But it mostly doesn't skip anymore. The yellow alignment lines are also off, so I added a little mark of my own to help line up the sight adjustment window. I don't think I'll ever fully trust this hub though...even though it's working, I still cringe in anticipation every time it goes to 5th.

Other things that are a PITA:

Many disc-brake compatible racks utilize the rear axle for mounting. With Alfine, my rack no longer worked. Still shopping for a good replacement. If your frame has two sets of eyelets, then no problem, but mine is getting pretty crowded around that disc caliper with my one set.

Speaking of the axle, you will now need to carry a 15mm crescent wrench with you in your saddle bag. And a multi-tool with some small pliers, because it's easier than finger for the cable. These tools can count as part of the weight total of the system, because you are not going to change a flat without them. Speaking of flats...

God help you if you ever have to change one in cold, sloppy conditions. First, flip the bike over into the muck; there is no way you'll extricate this hub with the bike upright. What do you think this is...a derailer and cassette? Ha! Next, use the pliers to remove the cable from the cassette joint. That's a real B to do with fingers in the cold wet, and not much more fun with the pliers. Then, 15mm wrench for axle nuts, and pull the beast out of your frame. Change flat. Now re-insert, carefully re-setting the counter-rotation washers, a task for which it helps to have the bike upright with the frame's weight on the axle. Now get down on hands and knees in the muck, and use one hand to hold the spring-loaded cassette-joint back, while either pliers or fingers re-insert the cable nut. Get all housing seated, and make sure the cable threaded the little guides and obstacles on the cassette joint properly. Back to your ride. Grind, grind, grind...what the #*@%!!! Bike back over to check. Oh, a little bit of grit got in the cable guide on the cassette joint, affecting the geometry of the wrap, causing my gears to grind again. Get the pliers back out, remove, clean the channel, replace again. Now, fingers raw, temper flaring, back to your ride, while you dream of how much more pleasant this kind of work is by comparison on a derailer system.

Do you like quiet drive-trains? I do, so no Chris King hubs for me, I suppose. Your Alfine, functioning properly, will make an unpleasant clack-clack-clack-clack-clack whilst coasting in gears 5-8, on the over-drive end of the roller clutch. Enjoy.

When this thing dies, I will not replace it with another. It will be replaced with a derailer system, as I would rather buy a new cassette, chain, and chainring every spring. But, it is a drivetrain that can work, and you can ride places on it. So there's that. I just don't think it represents an improvement over a cassette and derailer setup.

Shimano will also tell you that there is a whole host of activities it is not meant to handle, including: really cold riding, mountain biking, ice or snow, pulling a trailer, standing while pedaling, high rider power outputs, pulling a kid trailer, etc. According to Shimano legal-ese, the Alfine is designed for soft-pedaling casually on park pathways.

Do a Google search for Alfine hub skipping, and Alfine hub skipping in 5th gear. MTBR is rife with threads on this subject.