GameConnect Magazine have up a review of CS: Source, rating it a 9 out of 10.
Here's a quote:

"The first thing one will notice upon launching the game is the huge graphical upgrade from previous iterations of the series. Valve has been graphically improving its games for some time now; but after the higher-poly models released for Half-Life Deathmatch and Team Fortress Classic, the High-Definition pack released with Blue Shift and the upgraded map geometry and texturing in Condition Zero, the aging Half-Life engine has become a bottleneck. Valve has taken the freedom the Source engine brings and created new maps and models to breathe new life into an old game. The new grenade explosions are fantastic - particularly the flashbang’s blinding and dizzying effects. The changed weapon models may take some time to get used to but are uniformly excellent. Everytime, you can apreciate the fantastic Shaders effects, it is absolutely impressive to see how good is the lighting, brightness, water effects, real-time shadows....the engine is running perfectly. If Half-life 2 is that good, It will be hard to find a better game in the future."