Bloody hell, did not have any problem on the Demo or after i bought it via Steam.
But now i have big time lag after i installed the new patch!!!!! 
Maybe they should haved waited for the release, as it's full with bug's and the point-system/stats still is being updated.
5 patches/updates after less than a month 
Hope for a big update that fixes most of the bugs, as i don't feel like being a beta tester for a fully bought game
Wow... first of all "full of bugs" is not right. You don't know how much people running it without any problem because you always see complaining guys in forums, not the contented ones (or just a thousandth part).
Second: Why do you complain about developers that care about their customers, that care about bug fixing, that care about adding new features? Just because it won't help you in particular?
You would complain if there would have been 1 update, but this time "hell no, we need a fix, why don't you fix this or that?"
Third: beta tester for a fully bought game
-the game is 10$ that is AWESOME for such high amount of fun
Tell me a NEW game that costs even twice but gives you the same fun, please...
-being beta tester? there was a long beta time, just to make sure that you get a proper final
-most high-price games (i don't need to tell you titles, almost every is affected) even have critical(!) fixes before you get your hands on the CD/DVD
If you still think you made a bad purchase - well, you just might have bought the wrong game for YOU. Which does not include it is bad for everybody.
Sorry, but posts like this are just ... well, you get the point.
EDIT:
You stated that you did not have any problem before this patch. Fine.
Next you say THIS March 7th update made things bad. Ok.
Then you complain about many updates in one single months. Your opinion.
After that you hope they fix most of the bugs... Does not fit quite well, no?
Want to know about MY opinion?
Well, I do have some MINOR issues which could be better, but you always find those things. In conclusion every update made the game better, even my fps did not drop but raised by about +10.
Of course I can run HL2 with 200+ fps or CoD 4 or or or but if AudioSurf is fluid even with not such good fps, well, who cares?