I've got the older katadyn that you have to squeeze (can't sip) and it's definitely handier than carrying water, but took a decent amount of effort to get some water (you had to squeeze it with both hands pretty much). I see they have a newer one that you can sip on, so that may make it easier.

One word of caution is that it's not a water purifier. It'll get most cooties out of the water, but not chemicals or viruses. So use caution if you're around farmland. I use mine on backpacking trips as a backup in case my main filter goes out.