1. Google Maps is bad at Iceland.
Unshockingly, I'm a planner, and delegated the job of Route Mapping to Andy prior to our departure. If we hadn't been handed Big Map at the rental car station, though, we would have had issues. Maybe it's because many things in Iceland appear to have the same name, or because the Ring Road/Route 1, the road vaguely encircling the country, has segments that go by different names entirely. The bottom line is: rely on Big Map and the local maps available at gas stations throughout the region.
2. Lodgings are plentiful, at least in the not-quite-on season.
The compulsion to plan also led me to pre-book all our stays at hostels. Only in Vik might this have been an issue (that hostel was hopping!), but even so, for just a bit more money in the not-quite-on season, you can stay at a variety of guesthouses and farm stays sprinkled throughout the country. If we'd had a little more flexibility, we might have chosen to stay at one of them in a more optimal location. Or camped. Speaking of which...
3. There is a delightful national system of icons representing resources available at... well, basically anywhere.
Here's an example taken from a stop at an information center (itself signified by a big letter I):
That cloverleaf thingy? Bane of my existence. It means "interesting site," and they're everywhere, and I couldn't see them all. Hrmpf.
As a more specific example, the signs for guesthouses (which are often indistinguishable from non-guest farmhouses otherwise) often have a bed (lodging), a cookpot (kitchen facilities), a crossed knife and fork (restaurant/cafe of some kind), and one or more other icons signifying available amenities or activities.
4. Eating out is very, very pricey. Go for the bread and soup.
No joke, we saw $16 toast and jam on one menu. In many restaurants, there is an option for all-you-can-eat bread and soup buffet for somewhere between $10 and $15. Do it, if you're eating out at all (certainly not necessary when there are so many well-kept hostel kitchens around!). It's delicious and warm and filling and certainly cheaper than almost anything else you can get.
5. While parts of Route 1 do close for the winter and for especially inclement weather, "open" in some of the more northerly segments involves wending in your two-wheel drive manual subcompact up a mountain road that is occasionally covered by snowdrifts. In a blizzard.
I'd post a picture of this except that a. it was basically whiteout dotted with lava and b. I was too busy suppressing the urge to keen with tension (thereby distracting Andy, who drove like a champ) to actually take pictures. Also, there were geese happily poking about in the frozen wasteland, with no liquid water in sight, and it was a little demoralizing.
6. There is a national hotline for road and weather conditions.
For those who aren't stupid enough to assume that "open" means "not terrifying."
7. Frequently, signs are posted 100-500 meters before the actual thing they're indicating.
This has a great summary of Icelandic road signs (and the icons I mentioned previously). It does not mention the above fact, however, one that resulted in some minor travel delays ("OH GOD TURN RIGHT NOW DO IT too late turn around.").
8. Most towns have an expensive sundlaug and a cheap sundlaug.
One of the places we went swimming/hot potting had the motto "Swimming Is Quality of Life" emblazoned on the wall. Even the smallest towns--or farmstays/guesthouses--take that to heart, which is delightful when all you want in between the morning hike and the evening hike is a long soak in a geothermal hot tub. Many of the even very small towns have a spa-like facility to which admission costs $20-$30 per person. The public pools may lack the luxury (sometimes, although frequently they're quite nice in and of themselves), but they cost $3-$6 per person. You might even get to sit in on a community water aerobics class!
9. Particularly in the not-quite-on season, facilities open late and close early. Hike in the morning, then visit things, then hike again in the evening.
Example: leave for hike at 9 a.m. Return at 1 or 2 p.m. Feast. Heitur pottur. More hiking.
10. Skyr tastes like, to borrow the words of Matthew Inman, the souls of ten thousand unborn panda bears.
Seriously, how does a variant of yogurt taste that good? How? And where can I get more of it?
So yeah, Iceland was cool (no pun intended). Favorite points: towns composed of weathered clapboard buildings have awesome modernist churches, no exception (see: Blonduos, a particular favorite of mine); in the East, one must share the road with reindeer; and everywhere, the coffee flows freely. Here, have a picture of a lake with icebergs in it!