It sends a unique identifier to the server, and the server has access to the IPs that you connect from to post that info/check for updates. Depending on what they do with that information it could end up as a central repository of your bittorrent usage statistics (assuming you only use uTorrent and only run it on a single computer).
[EDIT] If you were downloading copyrighted content, and the RIAA/MPAA/IFPA/etc got a hold on this information they could use it to link your computer to an IP address (and even an IP address on at a certain date, if they web request timestamps are logged) by correlating the IPs associated with the unique ID recorded at the utorrent server with the unique ID stored in your settings.dat file. They could also try and use the Total Amount Uploaded/Downloaded since uTorrent was installed against you in court.
If you were running uTorrent in Wine, they could use that a some weak 'proof' that it was you downloading the torrents and not someone else. (If you run Linux/MacOSX/FreeBSD and have uTorrent installed in Wine; it's likely that that majority of uTorrent users are on Windows)
Most of the other stuff is rather innocuous. I can't think of anyway for it to harm you, but I'm not doing some sort of thorough analysis of it.
There is a beta version of uTorrent for Mac OS X, but it does not have a preference option to uncheck. It simply has "Check for Updates" -- no mention of "detailed information" or the ability to disable it.
uTorrent for OS X seems quite crippled, in terms of features, or at least it did when I last used it. I do get that it is still a work in progress. For now, I'm still using Azureus on my MBP.
