UL is always slower, in your Charter contract you will notice that your "speed" is only download speed (which is ok since that is what you do most), the advertised upload speed is somewhere around 500-750 kbs. Also in that contract, "Your speed will vary" and the folks at Charter say within 50% of the 5,000 kbs is acceptable. If you are getting slower than that, then call them because there is a problem somewhere in the line.
I think that nearly everyone got the upgrade a few months ago. The newer speeds are very nice... watching streaming video is now a very pleasant experience.