If you count the time before it's Steam release, I think I've been playing this game for a couple thousand hours.
First of all: The game is still called a "Beta", because the developers plan to add even more content in the future and don't want to call it a "full" game, yet. It is not some bug-haunted piece of software without any content to it, if you are afraid about that.
Secondly: You don't need to own any Source engine game to play PVKII. Just go to the Steam Store and start downloading it!
And as a third point: Some negative reviews criticized the unrealistic damage displayed for some attacks. The damage display is a plugin for "SourceMod" and has nothing to do with the PVKII base game. It is known that this plugin is not optimized for PVKII and sometimes displays improper damage. Therefore, most people use it only as a "hit detector" on certain servers.
Speaking of the game itself: It has so much love in it, you can see it everywhere: The voice acting is one of the best I've seen in a game - even retail ones. The voices and the beautifully crafted, slightly comic-styled models give each class a real "personality". The design of the stock maps fits the game's theme perfectly and the community has created a lot of good custom maps so far.
I have to admit that the population in the game is not the biggest, but it is always possible to find a full server or fill one quickly. The learning curve is steep and you will encounter many good players with hundreds or thousands of hours play time. While this could be frustrating for new players, it keeps the fights always challenging. In the end, the game is all about team play and even good players might not be able to win a game against a team working together really well.
The last thing I want to mention here is the rate of updates: There aren't as many updates as in other games, but it already takes quite some time to get into the game. You have to practice with each class for a while to be good with it. Creating classes and doing other major updates takes time. Especially since classes are not random models, but - as I mentioned before - real personalities and have a lot of references to literature and movies. There is also a lot of actual play testing by experienced beta testers involved before a release. This means that none of the updates has brought any balance problems with it so far. It always became better and each new class has been integrated really well.
I can only recommend to try out this game and want to thank everyone for reading my review!