As many on this forum will tell you, living in Summit County is not the idyllic mountain living many people dream of. We have a lot of strip malls, run-down neighborhoods, traffic, etc. But since you've visited, you probably know that. Having said that, living up here is still awesome. We have miles of backcountry trails practically in our backyard. Skiing opportunities abound (for both backcountry and in-bounds). Just waking up to this view is an inspiration to get up and be outside:
So here's a quick run-down of the towns in Summit County.
Silverthorne is the main residential town in the area (and with 3,500 people, also the largest), situtated mostly just north of I-70 along Highway 9. Unlike the other towns, 80% of Silverthorne housing is occupied by full-time residents. As such, there's more of a community feel in the town. Where we live, all the neighbors know each other and we often cross paths while out hiking, biking, running, etc.
Silverthorne's commercial area is however not the prettiest. There's no charming walkable Main Street. North of I-70, there are car dealerships, a Target store, more of a strip mall atmosphere. South of I-70, it is not a strip mall atmosphere, it is a strip mall, complete with McDonald's, Burger King, etc. But even in these strip malls, there are little gems of restaurants which I'll share with you once you move.

The commercial high-point

of Silverthorne are the outlet stores -- there are three distinct areas (villages) of outlet stores for Banana Republic, Nike, etc., that draws most of the tourists to Silverthorne. The town is trying to develop a central pavilion/shopping area, but it's still a ways off.
Living in Silverthorne is pretty nice, especially north of I-70 -- you're away from the main tourist traffic and crowds. The great thing about Silverthorne is that it is surrounded on two sides by Wilderness areas. The huge Eagles Nest Wilderness is the western boundary of the town, while Ptarmigan Peak Wilderness borders the eastern edge. Superb hiking -- you can be on the trail in minutes.
The cheapest area to live is an area called Dillon Valley East, which is just south of I-70. There are apartment complexes on Adams, Brian, and Rainbow. North of Annie Road are mainly single-family homes with some condo/townhome developments.
The other main residential area of Silverthorne is
Wildernest, which is actually in unincorporated Summit County. Wildernest has some townhome/condo developments (mainly off Wildernest/Ryan Gulch Rd) as well as single-family homes (mainly off Buffalo Mountain Rd).
Dillon borders Silverthorne a little south of I-70. Dillon is pretty small, and 75% are second homes or rental properties. Mainly strip malls on Highway 6. Dillon is also developing a Main Street area, but it also has a little ways to go. The main attraction is Lake Dillon (really a reservoir). It is very pretty. There's a marina in Dillon with a tiki bar. The Lake Dillon rec-path (paved) runs along the lake and is quite nice (does get pretty crowded on weekends though).
Here's a panorama from the rec-path that I took last week.
Just south of Dillon is
Summit Cove -- many people mistakenly think it's part of Dillon, but it is actually in unincorporated Summit County. Big single-family homes on big lots. Many full-time residents, but very pricey.
Keystone and
Copper are obviously the ski resorts -- almost nobody really lives there full-time.
Frisco is on the west side of Lake Dillon. Mainly strip malls on Highway 9 (there's a Walmart). Frisco has a pretty nice walkable Main Street though. Lots of restaurants and shops. This is the main place for tons of street festivals and fairs in the summer. Friso also has the new St. Anthony's hospital, as well as many doctors' office clustered around the hospital.
Frisco is about 50% full-time residents. It has a mixture of condos/townhomes and single-family homes. Very expensive to live, but if you want a walkable town, this may be your best bet in the county. The Lake Dillon rec-path goes through Frisco as well. The magnificent spires of the Tenmile Range rise on the west side of Frisco.
While Frisco is a nice enough town to visit, I'm not sure how nice it would be to live there, when almost every summer weekend, the roads are choked with festival goers and tourists.
Breckenridge is the other big town in Summit County. Because of the ski resort right in town, it is super expensive, pretty much out of the reach of mere mortals if you're looking to buy a place. They do have a very nice Main Street which runs along the Blue River. Although, after the 10th t-shirt/souvenir shop, you might be done! The whole town is a National Historic District, so it has that Wild West town feeling. Crowds and heavy traffic are common though. Breck is a bit set apart from the other towns in Summit County.
Only 20% of Breck are full-time residents. Although Breck has the new deed-restricted Wellington neighborhood, which is intended as affordable housing (affordable in Breck that is!).
There are other smaller towns, e.g. Blue River (S of Breck), and Montezuma (SE of Keystone). Blue River is mostly very expensive houses along Highway 9, while Montezuma is a tiny, dirt-road hamlet.
Many of the stats I've quoted come from a report published by
Shaping Our Summit. It is a very interesting read, and you can download the
full PDF report here.