ok, I just tried it out and I must say I am thoroughly impressed. I even dared and selected ALL and the backup took a few seconds!
One trivial thing (and I mean it when I say it's completely trivial): .htt is actually the best extension (HyperText Template). Especially if you have .html parsed as PHP on your server, in which case it would be more secore. .htt is also a recognized Windows extension, so for all intent and purposes it's just like HTML (eg if you dbl-click on a file it will open in your browser) but, as I said, more secure and designated for exactly what we're using it: as an html template
Chen ata gever