At home, I use a full headset from Plantronics. The SQ is great, and it ought to be, since it's a telemarketer-style unit that's very similar to the Plantronics I used at one of my jobs. It works great on my cell phone and my 900 MHz DSS cordless. (BTW, no, I was never a telemarketer, and I've never worked in a cube-farm call center, but I was a shipping-clerk/ customer service guy for awhile.)
I also have a Jabra Earboom in my glove compartment, but I never use it, because the people I talk to seem to have trouble hearing me. When I take my road trip later this summer, I'll be taking the Plantronics along. (I should probably sh*tcan the Jabra, but I paid money for that POS.)