There are only four "big" towns in Idaho. Boise area (Boise, Nampa, Caldwell, Eagle), Coeur d'Alene, Idaho Falls, and Lewiston. Boise is truly a big city, the others are around 50-100K.
Generally speaking Idaho is VERY conservative politically, but Boise is actually a fairly "hip" and modern town with lots of goods and services available for any type of person. It has very good weather generally, with fairly mild winters, but mid-summer can be pretty friggin hot. Humidity is very low though, so it's not as bad as the thermometers would have you believe. The economy there is in the tank because of the housing bubble, so house prices are incredibly low, but jobs are pretty scarce.
Coeur D'Alene is in the northern panhandle, in absolutely beautiful mountainous country, but the weather in the winter is gonna be snowy/wet for 7 months a year. Couple of really nice ski basins nearby if you're into that. Spokane, WA is only 30 minutes away, so anything you can't find in CDA is available there (concerts, big malls, etc)
Idaho Falls is on the eastern side of the bottom part of the state and is an "average" city in pretty much every aspect (not a bad thing). It's clean, comfy, and big enough to have goods and services for pretty much anyone. It's only a couple hours from Yellowstone and Teton national parks. It's colder in the winter than most places in Idaho, and summers can get pretty damn toasty, but it's quite dry there. In terms of "culture" (music, art, etc) there won't be much to see since they are so far from any major city (SLC, UT is about 4 hours away).
Lewiston is in the northern panhandle, on the WA/ID border. It's got a very mild climate, with hot summers, and is situated near mountains. At 700' elevation, it's the lowest point in Idaho, and the Snake River runs through there. The culture is pretty much non-existent, and there's a giant stinky paper mill there, but it's actually not a bad town. Hells Canyon (the deepest canyon in N. America) is just up the river, and there's lots of river activities nearby (fishing, jet boating, swimming, etc).
Despite the extremely conservative political nature of Idaho, the people tend to be very friendly and quite tolerant of just about any type of person. They have the classic western attitude of "You mind your business, I'll mind mine". It is an EXTREMELY "outdoors" oriented culture, and there is space enough for any kind of outdoor activity you could want (shooting, off roading, horses, hiking, hunting, and fishing) within an hour of any of the above cities. The majority of the central part of the state is wilderness areas, so if you're the kind of person who likes to lose themselves in the wild for a few days without being bothered by other people, you can't beat Idaho.
In short, Idaho is probably my favorite state. As mentioned, it has a huge variety of climates (desert to jagged peaks) and people (tree huggers to Nazis), and the space and attitude are ideal for anyone that relishes the freedom to move about and do your own thing. Unfortunately, Idaho's economy is in the tank like so many other places right now, so job opportunities may not be that good.
Good luck with your plans! Hope that helped.