Play Half-Life with friends! Players fight computer-controlled monsters through the original Half-Life storyline or hundreds of available co-operative scenarios. Also includes a plethora of new weapons, enemies, visuals and gameplay systems. Customization features allow each map to use its own unique weapons and enemies.
I'm not sure why there are so many 10/10's for this mod, but most of them don't even provide reviews. Sven Co-op is a brilliant concept that, unfortunately, falls far short of it's potential. In Vista, my friend experienced a problem where the game would minimize itself with every area load. These frequent map loads are greeted by MOTD screens, which proved to be very annoying and absolutely destroyed the immersion. At least, that is the default behavior, but we couldn't bring ourselves to play for much longer anyway.
I myself had been running in a 64-bit Linux distro on his brother's computer, and the music on the title screen didn't work, but it was otherwise fine.
The whole intro played out very poorly, but the worst of it was in the area leading to the chamber where the resonance cascade takes place. The scientists just started walking out of the room through the metal door, which our characters were also able to walk through. Eventually, they walked back through the door, activated the two-man lock system, and opened the door. None of the dialogue in the chamber played out. There was a five minute delay before the button at the top was unlocked, and it was about ten minutes before the cart actually showed up afterwards. Again, there was no dialog during this part, so me and my friend pretty much ate snacks while just wondering why everything was taking forever, and myself apologizing to my friend for coercing him into trying what I had believed would be a polished mod deserving of the 85% of reviewers providing 10's for.
When the cart finally did show up, I died inexplicably while my friend was transported to Xen, leaving me standing around in the chamber.
There was clearly a lot of work put into this mod, and playing through Half-Life with my friend would have been delightful, but it proved itself quite broken. If it works for you, great, but be warned that your mileage may vary substantially. Certainly not worthy of so much as a 9, much less a 10.