To use these, put them in your team fortress 2/tf directory, open up the console, and enter playdemo {filename}. SourceTV demos allow you to view the whole map, without artifacts commonly found on clientside demos.
You can cycle through different modes using space (default key for +jump), even though you might see a few glitches such as dissapearing weapons and stuff.
Smoothing works differently here, I haven't tested it yet, but the camera behaves nicer, so manual camera movement shouldn't be as jerky as the drive one in client demos.
The filenames also contain useful information. The form is: %d-%m-%y %H.%M-*H.*M *MAP.dem. Dates and times represent when STV started recording the demo.
The demo folder is pruned periodically by a script that deletes demos older than 5 days. Demos get downloaded off the TF2 server every 6 hours or so.
Also notice there's log files downloaded with each demo file. Those just contain periodical printouts of the status command, so they help if you're looking for a demo of someone.
If there's any problems with this system, don't hesitate to mail me at demos at mantaengie dot com
IMPORTANT - The demos will not open with the filename they have when downloaded. Simply remove any periods before the .dem. The plugin writes the hour and minute this was recorded in as xx.xx, and that screws up the extension. Simply rename the demo to something else.