Heard of SteamPipe yet? Welp, for those who haven't, it's Valves, sort of, new delivery system for all their Steamy goodness. Only, well, not quite all. Some of their older stuff, most notably the Orange Box games, were using the old system. Were being the operable phrase. They've now been moved across to, you guess it, the SteamPipe. For most people it doesn't mean all that much beyond improved download speeds. But for some, like those who use third part mods (so...all of us then) there are a few minor changes you will have to maintain compatibility across the board. You can see the whole FAQ in the link above, but the salient points will be listed below. Because I love you. So repay that love by leaving a comment.

• Authors and users of client-side mods (for example, those that require you to download a .zip and extract it into your installation folder) will want to switch to the new system for distributing and installing these mods.
• Users who make custom versions of game files (custom models, custom HUDs, etc) will need to make some simple changes in order to continue using those customizations.
• Gameserver operators will need to switch to the new download tool, Steamcmd, and be aware of how the changes to the filesystem affect any customizations they have made.
• Move the contents of your old tf/maps folder into the tf/downloads/maps folder in the new installation directory. For example, any maps you have downloaded will probably be found at [steam installation directory]/steamapps/[username]/Team Fortress 2/tf/maps.
• After the conversion process has run, copy the map files you want to keep (.bsp files) to a directory such as [steam installation directory]/steamapps/common/Team Fortress 2/tf/downloads/maps.