Ther is nothing wrong with using one of those, however, be careful to check the current capacity of the motherboard fan connectors. Most motherboards can safely supply anywhere from 500 to 1000 milliamps to each fan connector. Based on that, I wouldn't connect more than two standard fans to each fan connector. Be sure to check the amperage requirement of your fans to make sure that you are not adding too much current draw to any individual connector.
I was just recently asking my self the same question, The mobo should be able to handle the load of to fans on 1 fan header, I currently have to high cfm fans hooked into 1 head via Y splitter and been working good ever since. I'd say go for it, if your still worried, buy a cheap fan controller just make sure its 20watts or more per channel or you might run into issues on some fans.