Professionally I work with wireless under linux on pretty much a daily basis(Kismet, air*-ng, karma, etc.). I have found that the Atheros chipset cards are the most solid, followed by the Hermes. Unfortunately, these are uncommon as built in devices and usually have to be added as PCMCIA devices; and here I find their power....lacking. (Both of my Orinoco cards have about half the range of my on-board Intel 3945!) The Zydas chipset (found in many usb sticks) is coming along, but is still pretty flakey; I wouldn't trust it for day to day use.
Whatever you do, stay away from Broadcom. They are the devil. (Rat bastards!)
I've also had great success with the RALink usb sticks...they are cheap too, but no 802.11a. The Engenius EUB-862 a/b/g is awesome, being based on the Atheros chipset and pumping out about 200mw; but it is usb only and is about the size of a pack of cigarettes. (you attach it with a USB a-b cable)
So..I should stop rambling and summarize: