The osmolator rocks!!!! Stable, solid and performs reliably. As far as autotopoff they have very good products. You should PM Jhale. He has been using them for a while now. He does leave his tank unattended for long periods of time without incident.
I also use the autotopoff.com dual jammy. I picked it over the osmolator due to the far lower price. It works very well and is very reliable. You should soak the floats in vinegar every few months when you soak your pumps. Over time calcium buildup can cause float switches to stick.
I just purchase my A.T.O several weeks ago. Easy to setup. Recommended from Craig and several members here from MR.
Here is where I bought A.T.O from. http://www.reefexotics.com/topoff.htm