For the US, that meant either of the two models which have Bugaboo adapters: Graco or a Peg Perego. The problem was, all the Graco's we saw were fugly (I've seen some since that are OK), and the Peg Perego came with a base, which was a dealbreaker for NY taxi-riding. So I went online, found the carseats that fit Bugaboos in Europe, and met one of the best-designed carseats ever, the Maxi-Cosi Cabrio.
My main issue with US carseats was the size; they're all so damn big. The plaid and the giant canopies were also annoying.
The Maxi-Cosi Cabrio is sleek and light, and comes in clean, goodlooking colors and fabrics. [Of course, it also comes in lilac with zebra stripes or something, as if to prove that Europeans can have crappy taste, too.] We got Black Canvas, but only because it was supposedly available more quickly than Black Nylon.
When it arrived from Germany, the Cabrio definitely exceeded our expectations: good design and a small footprint; an easy-to-use manual comes in every possible language, easy to install with a shoulderbelt; nicely adjustable straps and buckle; the kid loves it. It even had two unexpected surprises: a secret compartment in the bottom (for the manual, it says) and a tent-like nylon sunshade which pulls out of the outer rim of the seat and loops onto the handle. Every carseat should have this.
Technically, a non-US carseat is illegal to use here, even though it's actually safer; EU carseat safety regs and testing are more extensive than the US, including requiring a side-impact protection system that most US seats don't have. But unless the fire department starts issuing tickets, or you're coming up for senate confirmation hearings soon, I seriously doubt you'll ever get busted.
[1/05 update: a lot of EU retailers have started saying they only ship to EU countries, including the two places above. But several people have had excellent getting their Maxi-Cosi Cabrio from babycare.nl, which ships UPS, publishes instant price conversions (the Cabrio's $178.51 at current horrible exchange rates), and is all in English (with Dutch for the adventurous). Personally, if I were buying it all over again, I'd steer clear of the canvas, which seems to age awfully fast.]
You can get The Bugaboo adapters came from Baby Concierge in the UK. German retailers like Playfactory (which I found via Amazon.de Z-shops have many more color options available; at around EU102, the Cabrio's cheaper on the continent.
Ultimately, I bought the Cabrio from Pitti-Platsch (Platypus in German), which seems to have the entire range of Maxi-Cosi for sale. (Look under Kinderschalen.) Depending on trim level, the Cabrio is EU120-130. Another piece of advice: give yourself a couple of months for processing and shipping, just in case. Or just carry one back on the plane.
02/2009 update:In the nearl five years since I originally published this post and these links, I've gotten email and comments from several people who had problems ordering from kiddie24, a German online retailer. And yet other folks have had good experiences in the same period. I can't tell what makes the difference, frankly. And it's hard sometimes to determine if an online store is a "real" company, with real infrastructure and follow-through, or just a web storefront for one guy selling car seats out of his garage. So before you order from random foreign webshops, search around, and contact the store in advance with specific questions about shipping, items in stock, VAT refunds, etc. That should give you at least some sense of what to expect--and it'll provide a paper trail for undoing transactions with your credit card co. if things go awry.