I've had this same issue for probably over 2 months now. Download speed is perfectly fine, upload speed varies anywhere from .25 mbps - 2 mbps on a good day, and that's with a 35/35 service.
It's most noticeable if using any kind of VOIP software like Ventrilo, Teamspeak, or Skype since transmitting voice uses your upload speed, and having no upload speed means nobody can hear you.