You really have to consider your cost of equiptment vs your use, if you just shoot as a hobby and occasionally need a polarizer or ND, than cheap filters may be the ticket. For general hobby use the may be just fine. Now if you are a pro, or making large fine art prints, the quality will be a much bigger factor. You can easily spend between $15and $200+ for some filters, you just need to consider where your needs end up in that range.
Anyway, based on your current equiptment and the price of the filters, I say give them a try, they may be all you need, and you don't end up nedlessly spending hundereds of dollars on filters. Or you may discover that you want something better, and resell the cheap ones for about the same price you paid.