I used to get the cheapest unbranded ones and always had problems.
Now that I got a good brand (dvico) I'm having no problems at all. Very professional. High quality, strong signal, tunes fast, universal driver API so you can use alternative software and OSes. (MacOS and linux)
If you're looking to save a few bucks, leadtek is supposed to be acceptable. I'm getting a USB dongle from them soon for my laptop.