Indeed. I thought it was a lot of fun, completed the SP on normal without difficulty.
Then I played expert a few times co-op. I'm not happy about the dedicated server bullshit (pings sucked, even mics were screwy), but the action was intense. It wasn't easy by any stretch of the imagination, and that's just the first 2 chapters. After about 3 different games, getting shot off servers due to shittiness and having the demo just kill itself randomly, I finally found a stable server/players.
Spoiler (highlight to read):
Took us 2 tries to get through the first chapter, but the 2nd chapter is rough, especially when you have to use all the medpacks to heal yourself off the bat. After 4-5 times of everyone dieing, we got the uber weak horde, with molitovs lining that last room. We all took auto shotties, but I'm quite found of the sniper (hunting?) rifle. Noscope headshots are quite lol, I emptied an entire clip into zombies attacking a friend in a stairwell. Worked nearly as well as a shotty due to noscope, semi-auto and aim
Maybe not worth $45 due to replayability, but it's a well developed game. Definitely worth the lulz if you've got some mates to play it with.