The mod adds a list of solid map additions to the vanilla version to run around in both in single-player and multiplayer. From the latest update description:
Client hotfix #1, for more info and changelog check Obsidianconflict.net
Due to the amount of time the Steamworks version takes, we decided to release hotfixes for the currently released version (1.35) to make the wait more bearable by ironing out some of the pesky bugs 1.35 has.
There are 2 versions;
One for dedicated servers, which contains the server binaries and improved mapadds,
As well as a client version which does not contain any binary files due to risks of possibly triggering VAC.
Even though personal tests showed that nothing happened yet running newer client binaries, we decided we do not want to take the risk since answers from Valve regarding that matter have been ambiguous at best, so do not get the hotfixes mixed up when you install them (no running the mod client with the hotfix server binary).
As mentioned before, this also contains a few improved mapadds, specially for some of the Half-Life 2 maps which got broken due to Valve porting HL2 and EP1 to the Orange Box Engine.
We are sure more hotfixes for 1.35 will follow to iron out even more bugs and probably even a full release at one point (like an 1.35b) which will allow us to update the client binaries without risk as well.
Below is the full changelog. Please note that even though most of these changes/fixes were ported over from the Steamworks version, this hotfix does not represent its current progress.