Chicco Keyfit 30
The Keyfit installs well in almost all vehicles, is relatively easy to use, fits even small newborns well and will generally last 9-15 months for average sized babies. It's on my 'generally recommended for most people' list :-)
Because you mentioned winter time, I'll take the opportunity to remind you not to use buntings like the Bundle Me in your car seat, or place snowsuits or heavy jackets on your child when s/he is in the harness :-)
The Keyfit is a very nice seat. The only drawback I find with it is that it usually causes parents to curse and swear at every other car seat they have to use after the Keyfit. It's probably the easiest car seat that you'll ever use.
(Of course this is not to say it's so easy you can skip thoroughly reading the manual - NO car seat is that easy).
We ended up picking the Onboard Air because we liked the air protect cushions, but it was a very close call when we narrowed down our choice. The Keyfit was a close second, and I'm sure we would have been quite happy with it if we'd gone with it instead.
I liked the Keyfit, but if I had it all to do over, I would have gotten the smaller version not the 30. DD was a carseat screamer so we switched to a convertible @ 4 months, and she was only about 16lbs at that point, so we never got anywhere close to 30lbs. The 30lb one is MUCH heavier than the 22lb one, so I would have gotten the smaller lighter one because there was no point to having one that my child never came close to the weight limit on.
I have a Keyfit 30 and I love it! It's so easy to install in any car I've ever tried it in, and it's a very cushy, well-padded seat. My almost 11 month old is 90% for height, and still has plenty of growing room. We got the "Graphica" one, and it came with a snap-on bunting. LOVE. In the winter time, we'd buckle her in snugly (no Bundle me's or any other after-market stuff around the buckles!), then tuck warm blankets around her, which were kept in place by the bunting. It worked wonderfully. The Graphica pattern is a little bit silvery. The main part of the car seat itself is black, and sort of soft and suede-like. Very pretty.