Basically, I'm in the market for a USB Bluetooth adapter. However, what's the difference in a Motorola one and a cheap eBay one? If the difference is noticeable, that is.

Thanks in advance.

The cheapo chinese ones are usually sub par electronically wise and wont last very long.
Make sure you get a name brand bluetooth adaptor that is:

Class 1
and bluetooth 2.0.

The cheapo ones most likely use outdated drivers and have problems with the bluetooth stack in windows.
I use bluetooth between My cellphone and my Carputer to allow me to use the carputer as a speakerphone, SMS/MMS reader and generator and caller id. I tried a couple of the cheapo units and they were really screwy and had horrible transmission distance. You're better off getting a quality unit, even if it is from ebay.

go to best buy. i think i got a linksys one or something. logisys? as long as you dont buy it on ebay it prolly doesnt matter. I assume you're downloading shit to your phone? i can get you the name of mine if you want, but it was $50 as well. My thinking would be
ebay=shitty.
motorola= only works with your phone.
linksys (or whatever)= can work with your phone and whatever else you get thats bluetooth in the future.
EDIT:
http://www.bestbuy.com/site/olspage.jsp?skuId=7424227&st=usb+bluetooth+adaptor&type=product&id=1124431844886
it was a kensington. lol. i was WAY off. but thats the one i have. looks like it came down in price a bit... :( works great for my razr. Cant beat $35 compared to $50 for the motorola one right? :shrug

Alright, thanks for the input, guys. :)