I've used several of the smallest versions of this for my 2.5-10g tanks.
Quieter than an HOB filter by far, they do tend to take up quite a bit of space in the tank. "Unsightly" is subjective, and dependent on your scaping. The dark color blends well with a black painted tank back and I found it pretty easy to obscure mine with a combination of driftwood and plants. I also liked the flexibility offered by the multiple rotation options on the outlet head. Keep in mind the actual dimensions of the unit as well--it can look deceptively slim in photos, but they actually take up quite a bit of space in the tank.
However, the one problem I had is that the filters--at least on the small versions--are pretty much impossible to rinse out well as the actual media is surrounded by non-flexing plastic making it impossible to squeeze out any of the debris. I still use mine--but have replaced their filter catridges with custom cut blocks of foam that I can clean without losing beneficial bacteria.
Last edited by Knotyoureality; 02-05-2013 at 08:11 PM.