You could already schedule new recordings and set up season passes on your TiVo from a browser, but now you can actually manage those season passes without having to trudge through TiVo's onscreen menus.
I recently cleared out my old season passes in preparation for new TV shows and discovered I still had shows like Heroes still there. Freakin' Heroes! I stopped watching that back in 2008! If rearranging the priorities and deleting shows didn't involve a Herculean trek through the netherworld of TiVo's user interface, it wouldn't be a problem. So yes, this new web interface is great.
(After making the above video, I realised I didn't actually clean out those shows after all. I just thought I did, and probably stopped because it was such a hassle to delete each one individually. Which proves my point even more!)