Once the initial load is done, all the updates are done via AJAX (well, JSON, not XML), so will feel snappier (no full page reload required, it's only a few kilobytes of data which is used to update the page)
Can it be that the heavy upload cause by uTorrent blocks the upload from the web UI?
This is unlikely if it's slow over your local wireless network - it should be able to transfer about 1-5 megabyte/s, unless you can upload at that speed it's unlikely to cause noticeable slowdown. Over the internet, yes, too high upload speeds (saturating your upload) will cause everything to slow down a lot (as Slink84 says, you should limit uTorrent's upload speed to about 20kilobytes/s under your max upload speed)
Does it happen even when no torrents are running?
Have you tried connecting to the machine in other ways - such as the Windows file sharing, or something like XAMMP (a web server) - if these are similarly effected, it's not uTorrents fault, but some other factor (the router, perhaps?)
Another thing to try is
telnet [uTorrent machines IP] [web interface port] then enter