I have the 5 gal, had it for 1 year or so.
Quiet filter, works fine for typical community tank inhabitants, nice in that everything is contained inside the tank, without anything hanging out.
No yellowing of the acrylic noted yet, but one major drawback to any acrylic tank is scratching. We have hard water which leave deposits on the acrylic. These are almost impossible to get rid of with just a sponge. Using even the softest scrubbie (supposedly for acrylics) left fine scratches over time. These are getting noticible after 5-6 months. I would immagine that in a few years, it would be quite clouded with scratches.
For long term use, I think I owuld stay away from acrylic. I remember seeing larger Eclipse tanks (20 gal?) that are glass ... maybe better buy in the long run. Alternative would be a small glass tank with an internal filter ... almost as clean looking & efficient as the Eclipse.