I've been using three T-90s for several years now as part of my 15ish dish farm. Everyone seems to have extreme reactions to them. In my case I took down two motorized 1.2 m GeoSATpro offsets after installing the T90s because they offered nothing of value. Admittedly I still have a motorized 1.8 m offset used very occasionally for weak Ku feeds, and a 2.6 m Birdview for way-out-of-footprint reception games. The primary benefits I've seen with the toroids are immediate access to any satellite from multiple receivers, and complete immunity to high wind. The 1.2 m mounts were too flimsy to maintain lock in fairly typical wind for here, and when coupled to even heavy-duty DiSEqC motors, they were even worse. At one point I even tried a C-band HH motor on a 1.2 m out of desperation, but it got shredded in a rather nasty storm. When adequately crunched down, the T90s remain fully operational in the worst Mother Nature throws at them.
In terms of sensitivity, I have to disagree with others. In a post way back, I provided test results from a very careful comparison of sensitivity across a T90's arc, and then to a 1.2 m as a reference. In the center few degrees the T90 outperformed a 90 cm dish, and was very close out to about +/- 10 degrees. By +/- 20 degrees, the the gain was only comparable to a 76 cm dish's performance. Thus I use three T90s, generally sticking to the center 20 degrees on each to cover all FTA Ku birds from 72W to 127W. We also subscribe to Dish Network and Shaw Direct (Canada), and given those satellites are more powerful, I have easily covered everything from 61.5W to 148W at one time or another with the same setup.
I normally have 25-30 LNBs running off the T90s. The main downside from that is the cabling and switching required. That favors bandstacked LNBs, and I have a truckload of Superdish and Sadoun units. The feedhorns that come with Superdish LNBs are small enough to work with 2 degree spacing on the T90s, but the sensitivity is lower than I would like. I solved this by bolting on full-sized horns, but that causes spacing problems. Originally I sawed off the edges, bolted two together in pairs, and sealed them with caulk. Recently I discovered I could simply take off a little metal with a grinder, without compromising water-tightness. I wish I had realized this before.
Aligning the T90s is a little different than a typical Ku dish, but it only took me a few minutes to get the hang of it. I am an extreme perfectionist, and found I could nail a better alignment in less time than on a fixed Ku dish, partly because the T90 mechanics are generally better. When compared to a motorized Ku dish, this was a walk in the park. Even nicer is I have never had to realign the T90s, unlike my other offsets, which needed occasional touch-ups because of twisting and bending in the wind.
The bottom line is we have six locations in the house that can instantly switch to any channel on any bird with simple remote control. The toroids allow direct access to all North American FTA satellites, along with those from Dish and Shaw. When I'm looking for a feed, I can blindscan simultaneously on several PC tuners without having to move a dish, and cover the entire Ku arc in minutes. The only alternative would have been 25+ 90 cm dishes, which would have caused far more brain damage. Given that most people appear to have problems getting T90s aligned and don't want to deal with multiple units, switching, and 2 degree spacing, I generally only recommend T90s to experts who are willing to think out-of-the-box. But I never would go back to the 1.2 m offsets. They were junk and next to useless by comparison.