If you want to download the next Ubuntu release (10.10 – Maverick Meerkat) faster, you could prepare yourself, getting first the Release Candidate.
That will ensure you that you’ve got the 95% of the final packages already downloaded, and in the final version, you will have to download only a fraction of the data.
One trick you could try to get all the benefits, and none of the drawbacks could be (I’ve not tested it yet, so don’t blame me if it doesn’t work for you):
Even, you could start the upgrade, let it download all the release candidate packages, but stop it before it actually make any changes to your system.
Then, you could wait until the final release, and then start again the upgrade, profiting from all the already downloaded packages.