I went with dimmable CFLs in my basement. I had approximately 15 cans on one switch (and one other smaller section with approximately 8 bulbs on its own switch) and although I bought a 1000 watt max dimmable switch, the wattage (60w x 15 = 900 watts) would result in the switch becoming very warm to the touch. Also, the heat generated by all those bulbs made the room too hot. There are GE 15w CFL dimmable bulbs that look exactly like regular 60w floods (the spiral light bulb is inside another glass bulb that is identical in shape to a regular flood bulb). They sell at Walmart for about $12. I think they come with a 5 year guarantee, but I never keep receipts. I think I have had one burn out in about 2 years. I never see these bulbs for sale at Home Depot or Menards, but Walmart has carried them for years. As another post above mentioned, it does take a minute or two for the bulbs to get to full brightness, but once they're lit you would never know you're using CFLs.

Use the LLF LED bulb for your 6" cans. They're more energy efficient, more environmentally friendly, can be dimmed and will last 50k hours. The color quality is great as well. They don't have a 4" version yet. So you're out of luck there. As for the CFL's. You'll most probably have to take out your dimmer if you use them. Even if you don't dim it, you can have some problems. The can you have is probably rated for at least a 100 watt bulb. A 40 watt fluorescent should be fine. Can't help you with #1 or 4 though. Sorry. Anyway, go with the LLF. It's pricey (try calling the places rather than ordering online, you might get a better price), but it's so worth it. They only have one product now- the LR6. But I tell you, it's fantastic. Here is a link that might be useful: LLF's website.

There really isn't a cure-all type of bulb that does all of this well, so you're stuck seeking a compromise you can live with. If you absolutely must have all these lights on dimmers and aren't willing to try some dimmable fluorescents then your options are very limited. Essentially you've just got to choose between a few types of incandescent bulbs. The fixtures and trims should have little stickers inside that list the bulb types and maximum wattages you can use. Most likely, you'll be choosing between basic incandescent "R" type reflector bulbs and halogen "PAR" bulbs. Both are available in a range of physical sizes (R20, R30, PAR20, PAR30, etc) and wattages. Both are fully dimmable and provide warm light that renders colors well. The "R" type bulbs will produce somewhat softer light and be more forgiving of poor can placement. Unfortunately they are also the least efficient bulbs you can easily get your hands on, meaning you'll have to use higher wattages to get enough light, therefore pumping more unwanted heat into the house. They'll also burn out quite frequently. The "PAR" type bulbs, being halogen, are more efficient, producing less waste heat than R-types, and won't burn out nearly as freqently. They produce light that is more crisply focussed, with more tightly defined pools of light, brighter surfaces and deeper shadows. Because they were initially developed for outdoor use they have very thick, shatter-resistant glass around them that heats up and can feel like a little radiator - the "heat lamp" effect. In other words, the bulb type that actually puts less waste heat into the house feels like it's heating things up more. I've heard good things about a hybrid type of bulb, made by Westinghouse, called "Halomax." These are halogen bulbs, so they are more efficient and last longer, but are not intended for outdoor use so their glass isn't so thick. Their light distribution is likely to be similar to the R-type lamps, and I'd bet they don't have so much of the radiant "heat lamp" effect either. You may have to order them online if a local company doesn't carry them. You might want to buy several bulbs of different types and wattages and experiment.

http://nehomeenergy.unl.edu/web/homeenergy/CompactFluorescentBurnOut http://www.energystar.gov/index.cfm?c=cfls.pr_cfls_about ("Give them air" near bottom) From Techniart FAQ's: Can I use my CFL in a totally enclosed fixture? Before using a CFL in a totally enclosed fixture, you should consult the product packaging. CFLs that are not designed for totally enclosed fixtures will typically carry a disclaimer that indicates that they are not intended for this type of application. Because totally enclosed fixtures do not allow air to circulate around the lamp, it causes heat to build up, which can lead to performance issues. Though CFLs do not produce nearly as much heat as incandescents, they are more sensitive to heat, which can effect their performance. Some of the components in a CFL can not withstand high heat, unless specifically engineered to do so. The excess heat that is created in a totally enclosed fixture can cause the light output to be diminished, the bulb to appear to "dim" more quickly than CFLs used in applications that allow airflow, and a shorter bulb lifetime. The most effective way at this time to ensure that the particular product you are interested in purchasing is designed to withstand high-heat applications, is to check the packaging or contact the manufacturer directly. Now I'll look to see if there are bulbs specifically made for enclosed fixtures.