That EcoSmart bulb (also known as the Cree CR6) is probably the right answer for your needs. Yeah, it costs more than the A19 traditional Edison bulbs, but it mounts flush and looks good. Nice bonus: I believe it's "damp rated", meaning you can use it in bathrooms and such.

Any 6" ceiling can should be just fine for any Cree downlight. For my own house, the 6" cans all had a spring-loaded front cover that I had to remove, and also the Edison socket was mounted (poorly) in a metal plate that clicked into the can. I had to remove the sockets from the plates, so that all was left was an Edison socket dangling from its wires. At that point, you just connect the socket to the bulb, flip out the metal flanges, and shove the bulb into the can.

Note that some Cree bulbs have a GU24 socket rather than an Edison screw socket. At least when I bought them (Cree LR6-DR1000's, several years ago), they came with a GU24 socket in the box, including all the crimps you need to connect them.

If I was truly starting from scratch, I'm not sure how I'd want to do it. The world of 12VDC MR16 LED bulbs is coming along nicely, but they're expensive. There are also a bunch of fixtures these days that have permanently installed LED lights, assumed to last the life of the fixture. I'd be tempted to go with those, if I could find ones that I liked.