Regarding description, one thing to consider is why the long descriptions are there. Certainly in some cases they are used to pad out the length of a story to stretch a novella into a novel, but in many cases authors actually do have a purpose in mind.
For example, in S.M.Stirling's Conquistador, there is a point in the novel when the protagonist is invited to lunch at the estate of the founder of one of the alternate reality kingdoms. Stirling spends a couple of pages describing the estate -- the driveway up to the house lined with trees, the white gravel of the parking area, the gardens, etc -- followed by nearly a page detailing the spread of the buffet-style lunch. Now, if you're not into description this could easily appear to be superfluous and even annoying, but there is a point to it.
Despite occurring in the present, this landowner is living a lifestyle analogous to the antebellum South in the US. He isn't just wealthy, he is literally the lord of all he surveys. There are only about a dozen family/kingdoms running an entire planet, and he's the guy who started the ball rolling. The world is not completely without politics and internal strife, but those are more about global policies than who controls what territory.
So if you find yourself bogged down by the description, or find that the action moves very slowly, that is actually the point. Stirling wants readers to be slowed down, in order to engender a feeling of peacefulness and lassitude. Then, when the plot's conflicts start resolving, the reader feels the loss; it's not the end of the world, but it is the end of peace.
Reading Mr. Martin of Game of Thrones fame I notice he will describe a characters clothing down to the underwear.
I'm not certain what Martin's influences are, but given his background this might be an allusion to Chaucer. Geoffrey Chaucer's The Canterbury Takes is probably the single most influential book ever published in the English language. I know that sounds odd given that most people never even hear about it unless they study English in University, but it's true. When the Tales were published in the late 14th Century, English was the language of peasants; scholars studied Latin and Greek, the nobility of England spoke French, and England in general was considered a bit backward culturally compared to the rest of Europe, so most entertainment was in French, Spanish, and Italian.
As for how this connects to Martin, Chaucer goes into great detail talking about the clothing and dress of all of his characters. Not just what the clothes look like, but the fabric they are made of and where they were made. There are two main reasons for this.
First, there are a lot of elements of satire in the Tales, and the Sumptuary Laws (basically, what you're allowed to wear is dictated by your class, not what you can afford) were a major element of class dynamics. By describing dress Chaucer was denoting class; moreover, by using inappropriate dress he was drawing attention to those characters, such as the "poor" priest wearing fine clothing, paid for by selling indulgences.
Second, in addition to being an author and a court clerk, Chaucer spent several years as the comptroller of customs for the port of London, and fabric would have been one of the primary luxury items being imported. So, when Chaucer wrote in detail about clothing, it was because it was a highly specialised field of knowledge about which he knew a lot and clearly enjoyed. In other words, he wrote about what he knew.
So, maybe Martin himself also has a personal interest in clothing, or perhaps he ran across a good database of medieval outfits when doing research and enjoys using it, or perhaps he's just emulating elements from Chaucer. Similarly, a lot of the odder story structures in The Lord of the Rings are the way that they are because Tolkien ignored the past few centuries of literature to focus on older works like Beowulf.
So to get back to @philhebe's original question, when considering description you don't just need to consider what the character would notice and describe, but also what is your reason for the description and your focus as an author? If you personally do not use a lot of description, then perhaps you might want to try doing so just to expand your skills. On the other hand, you may prefer to write in a crisper, more action-oriented style and eschew description.
If you want see a really freaky example of minimal description in a published novel, check out White Jazz by James Ellroy. Anecdotally, when Ellroy's publisher complained about the book's length, he stripped out all of the verbs and sent it back. The actual finished product is gripping, but very strange; Ellroy's prose has a staccato style that keeps the reader going at an almost frantic pace, despite not really knowing what's going on most of the time.
