1. There is a company in the US making a bar end shifter for hub gear. I thought you could get it from SJS, can't find it quickly....
2. SRAM, Shimano, Sturmey-Archer.... There's all sorts. My boss just set his new bike up with a SRAM 3-speed and a Schlumpf Speed drive BB gear, to give himself 6 speeds.
3. I have hub on my winter hack, derailleur on the summer one. It's hard to compare because the winter bike is just heavier all round - chunkier wheels and tyres, hub brakes, more clothes/fat on me

, etc. I don't imagine I would notice much though. The biggest difference is remembering to alter shifting tactics for the derailleur - making sure I'm in a low gear to pull away before I stop at lights and so on, instead of stop, click, click, ready to go.