carrado: I had a somewhat similar list of things I wanted in a commuter but with a more specialized purpose: winter
This is what it turned out like:
The frame is a Mongoose Sabrosa and it was meant to be set up in a few different configurations. It could be single speed, derailleur based, or IGH based:
I wanted a winter bike which meant it needed clearance for some bigger studded tires so I ended up with a beefier frame than you might be looking for. This came in well under $1,000 but I built it up from parts (some of which I had lying around). The frame was $25 from Nashbar's frame sale.
I don't have a recent picture but there have been some changes. The fork I had on there originally was something I picked up for $15 and was aluminum with a limited travel head shock. It had the dimensions I was looking for so I grabbed it. I eventually replaced it with a carbon fork similar to the bike in the second pick. Although you can't see it well in this picture, the original IGH was a Nexus 8 speed "Redband" and I had a roller brake on the rear. The front brake is a BB7 (disc).
The shifter is a bar end from Jtek and I highly recommend it if you are going to use a Nexus or Alfine with drop bars.
Anyway I have real world experience with roller brakes, Nexus/Alfine Hubs, and disc brakes.
Roller Brake Pros: Super easy adjustment, quiet, works in all conditions, low low maintenance
Roller Brake Cons: Not the quickest stopping brakes on the planet, heavy, experienced drag from grease in extreme cold
Disc Brake Pros: Relatively light, work in all conditions, can remove wheel without disconnecting anything, stop fast
Disc Brake Cons: Squeal like banshees if something gets on the rotors or pads, tight clearances between pad and rotor means rubbing if something is out of whack
The Nexus 8 speed Premium or "Red Band" and the Alfine 8 are virtually the same except that one works with roller brakes and one with discs. First off I will say that I'm very pleased with it. It shifts smoothly and it's super quiet (something I like), even while coasting. The range is adequate for my needs. People use these things on off-road bikes because they aren't as susceptible to getting gummed up or broken as derailleurs are. I like it because it's not affected by ice, snow, or grit. Grit and ice used to do a number on my derailleurs in the winter.
IGH Performance: This is truly hard for me to gauge. I would not choose to use it on a fast group ride or in any kind of road competition. It's not that I feel there is a huge loss of efficiency but spacing is not as close as I'd like, - especially between 5th and 6th gears. At the same time I don't feel it slows me down much at all on a summer commute. In winter you get some drag in cold weather. I switched from grease to ATF (transmission fluid) and that has helped.
IGH Weight: Somewhere in this thread someone said they replaced their derailleurs with a 7 speed Nexus and couldn't really tell the difference. Maybe the 7 speed is a lot lighter or the original derailleurs and cassette were on the heavy side but in my experience the Nexus/Alfine is quite hefty. Maybe on an otherwise heavy bike it wouldn't be noticeable but on this bike there is a substantial rear weight bias due to the hub. It's kind of annoying when you pick up the bike. How much does it affect performance? Well, their are all sorts of arguments about weight and performance that I won't go into, but if weight is a big concern, you might be bothered by the Alfine (or any IGH with more than 2 or 3 gears).
One last note about brakes. If you want a brake you can set up and then not have to worry about at all for a long long time, a roller brake is a very good choice. If you care about weight and you want the best stopping power in all conditions, then discs are a very good choice.