...you might want to read the excellent review written by Andrew from Webupd8 (including a video). Although as said before Andrew won't be giving all the details of every new feature since most have been using it for a while but ... it's well worth a read/"view" though.
I have nothing to hide, I'm a bit scarred by Canonical these days and usually I'd just go ahead and download it. But this time I'm gonna do it slowly.
Anyway, not just Ubuntu, usually any famous distribution, within the first days of their release sometimes (especially if you have a very fast internet connection) you may not be able to achieve the best possible downloading speeds due to the massive "traffic" these servers get.
And on the other hand, usually what happens next is that, while downloading if you got disconnected or something happened to your download, even though the software says the server supports "resume" capability.. yet most of the time (happened to be with Ubuntu, Fedora and Debian, recently that is) when you try to "resume" the server simply refuse to do that!.
So unless you have a very fast internet connection that usually takes about 4-5 minutes to download a 700MB CD image.. I highly advice you to try the official Ubuntu 11.04 torrent channel first. It may take a few seconds for the Bittorrent manager to get into the full throttle.. but the advantage here is that you'll always be able to "resume" your download no matter what! (more than handy if you have bit slower internet connection).
And you can use the Cloud computing feature that Canonical has been sneaking around :P in the recent times (very smart move though), which basically lets you to try Ubuntu 11.04 Natty Narwhal without having to download (click the link). This is only available for 55 minutes.
Although there is no official document telling what the hardware requirements other than Canonical saying...
"Ubuntu 11.04 is built to take advantage of the very latest technologies, but it should work on a most desktops, laptops and netbooks too..."But I did write a post about the requirements of Ubuntu 11.04 Natty Narwhal from the bits and pieces that I "collected"(more than welcome to correct me if the hardware requirements of that post aren't that accurate).
Note: - But remember, unless you have a reasonably faster internet connection... don't judge the "speed" of Ubuntu based on this cloud test run. It's not fair for the hard work of the developers. And lastly, congratulations Canonical for this amazing achievement. Finally, something of your own, and thank you for making it free too :).