I have an MSR filter and I'm not happy with it, way too slooooooooow, my Dad has the one from Can Tire (can't remember the make, it's off white with blue letters) and it works great, pretty fast, around $65
I've had beaver fever twice, it sucks but doesn't kick in until 2 or 3 weeks after your trip, if you get it, ask the doc for Flagil (sp?), it works quick