The cat and dog love the fresh water
When i bought this, my wife was saying i was crazy. She swore that they wouldn't care if it was fresh daily, or always fresh. So, we left the bowl that she filled daily with water out as well. It took the pets about a day to get used to the fountain but, once they did they didn't even touch the water from the bowl.
The downside is that it does have a little bit of noise... soft at first but, like a kettles loud whistle to tell you it needs attention. So does this, with an annoying gurgling sound.

love my cats
My 3 cats love the Pet flow I had the medium but that was always empty so I gave it to my mother in law and bought the Jumbo and that last alot longer the cats and 1 dog drink and drink. I may alittle noise form the water hitting the bottom but that is ok I don't mind it as long as they are all drinking I can deal with it. love it.

Cats love this fountain
I would recommend this to anyone with a cat. This is the second one I have purchased. The first one I had given to a friend after my cat passed away three years ago. When I decided to adopt another cat, I bought one for him, and he loves it as much as my first cat did. It really seems to encourage them to drink more water, and it functions quite well. I would recommend changing the filter at least once every 8 weeks, and cleaning the whole fountain at the same time. The only down side is that I have to fill the reservoir at least every 24-36 hours. If you have more than one cat or are gone for two or more days at a time, you may want to invest in the larger size.

Wonderfully Whisper Quiet!
This is the third pet water fountain I've owned, and the best. The first one was the very large size,with large resevoir attachment. I think it was too much water for my two cats - they didn't go through it fast enough so the water seemed to get "stale". I eventually ended up getting rid of it because all of the nooks and crannies inside were too hard to get clean and ended up slimy and gross - I wouldn't want water from it! The second fountain I had was a Medium Petmate - but the "deluxe" model with adjustable fountain speed. This one was very noisy and I always had to fiddle with it to get the water pumping correctly- often in the middle of the night so I could sleep. (Eventually my cat puked in it, jamming the motor. No desire to try to fix it). I had given up on the water fountains - even though my cats LOVE THEM- and then this simple model went on sale. It is perfect. I have to refill it often - may be a downside for some but I figure my cats are getting fresher water this way. It works great and I can't believe how very very quiet it is. Maybe simpler is better!

Great Idea with a weak and flawed pump
I've now had this fountain for a little over 2 months and the pump is starting to fail.

As is, if I unplug it, to start it again I need to open up the pump and push the impeller to get it spinning. Without the initial push to get it running, it simply doesn't start.

Also, do not think that this fountain will replace your water dish or be less of a hassle. In fact, this will require a tremendous amount of effort to keep running.

Daily Maintenance:
Clean out cat/dog hair from the mesh.
Fill up.

Every Other day:
Clean the inside filter.

Weekly:
Take completely apart, wash out all gunk, hair, dirt etc.
Open the pump, push the impeller to get it started.

Oh and both the cats and dogs seem to prefer the old large water dish as opposed to the fountain, which they also use, but not nearly as much.