This is true not only of PetSafe products, but all products.

The plastic is susceptible to getting small (I'm talking microscopic) scratches in it from normal use, and these scratches often have bacteria stuck in them. Because they are so small, they are very hard to clean, which means that over time the plastic will be less sanitary.

A few of the products that I know of and have seen at work are the Avalon and the Pagoda, both of which are ceramic fountains.

One other option that I will mention that might not be initially obvious is the Everflow. While this fountain is still made of plastic, it is a different grade of plastic that is designed to be more durable, allowing it to be used outside (though it can still be used inside). One added bonus of this is that the fountain is much tougher. This model also has a water recirculator in it (in the picture, it is the grate in the bottom of the drinking area) which keeps the water moving, helping to prevent grime buildup. This feature made it's debut with this product, but is being incorporated into future fountain designs (so far as I know).

If you haven't gotten one yet, I may be able to help you out a little bit. My personal choice would be the Everflow or one of the Avalon or Pagoda fountains. The two ceramic fountains cost a little bit more, but they will be more hygenic than any plastic fountain and they are much better looking IMO. The Everflow will work better for a larger pet (like a Lab or a Golden) and is durable enough to be used outside (it even has hose hookups on either side so that you don't have to worry about filling it up). I worked with the Everflow a lot, as we were looking at the type of plastic to use when I worked there last summer, and it is a fantastic design. Very durable. My only complaint is that the top housing may be a little tough to remove, but once you take it off 2 or 3 times, you get the hang of it and it's not difficult at all.