Well,
First of all, if you have an issue on k2 you should give more info to let users help you and post on the right forum.
My suggestion, before say words like "k2 doesnt works properly" you should look yourself and be sure that you have everything working good on your site, or everything configured how it should be.
K2 works like a charm, and there is a stable version which works very well.
OpenSource is what it is, and give thanks for such a good products are FREE.
If for some reason you dont like OpenSource just get to buy a comercial solution.
Didn't solve your issues?? Why dont you consider hire me? Email me or contact me www.xevedigital.com for details