Torrented S2 the night it was released and it came down at a very heathly lick. Plenty other people did so too; it doesn't need everyone, or even most people to use the bittorrent download method to make a noticeable difference to the load on a server.
In any case, the LFS chaps will have plenty mirrors arranged in advance so creaking servers hopefully shouldn't be an issue.
However, this is exactly the type of legal application where Bittorrent excels; its silly not to use it if practicable to do so.
Note that recently ISP's are moving towards traffic management of P2P protocols. Pipex for example limit _all_ P2P users _all_ of the time to around 20K download speeds. Very unfriendly, and just a tad draconian.
Happily, you can usually circumvent traffic management by using the protocol encryption provided in the latest versions of utorrent, Azureus and BitComet. Just make sure you enable it