I for one am happy the raspberry pi team isn't delaying their release to fiddle with wifi. The regulatory non-sense can literally take years per country.
I'd recommend Atheros arl9170 instead.
Simply using the built-in drivers in ubuntu or a prebuilt module from ralink yields an almost unusable link.
You have to be on your toes and willing to compile your own drivers (and even learn about the source and make tweaks) to really get ralinks to sing. The good news is that ralink makes this source freely available.
Atheros's work great but they cost more (like $15 or $20 instead of $7) and you still have to be careful to get the right "mad-wifi" drivers. There are less of them though and most versions work out of the box at least acceptably.
Your advice is sound though if you're just looking to get your one ras-pi on the air with minimum fuss you probably want this : http://www.amazon.com/TP-LINK-TL-WN821N-Wireless-Adapter-WPA...
If you're preparing your robot army for world domination on a budget, its probably worth putting in the time to figure out a ralink. I've had great luck with this sub $7 beauty http://www.amazon.com/150mbps-Wireless-Adapter-Wifi-802-11b/... but it did take considerable effort to hack the driver into shape.