John, I own the F4.55 version of the 11 inch ELT and have been very happy with it. The Zambuto mirror is superb, as you have undoubtedly heard or seen. I do think the scope could use a fan to deal with getting the mirror to the ambient air temperature and get rid of the boundary layer that can affect the qualuty of the view.
Mechanically, the scope is nice, with smooth motions but a bit of friction that allows a fairly wide variety of eyepieces to be used without any balance issues. It is balanced for a Parracor, and I have used everything from a 26 Nagler to a Nagler Zoom without having any balance problems. I have also found that the four pole structure holds collimation well as you move up and down in altitude, despite some reports of collimation shift due to the lack of a true truss structure. I kind of wish the mirror box and rocker base used nicer joinery (e.g., like a Telekit), but the scope has held up well with no sign of anything loosening or otherwise needing attention.
For me, the scope has offered outstanding optical quality in a very transportable package that is about as much scope as I want to deal with in terms of size and weight. The relatively short focal length allows for seated viewing throughout the altitude range.
I typically keep the scope assembled at home, and carry it out to my observing deck (up a hill) in two pieces, the ground board and rocker box first followed by the complete mirror box/pole/UTA assembly. For travel, I take out the poles to allow a fairly compact package that fits easily in the back seat of any car. The four-pole structure with the Moonlight connectors on both ends makes for very quick assembly.
I've got one of the F/5.4 versions of this scope. Overall its superb. The pieces are a managable size and weight, and it goes together very quickly. Optics are superb -- one of the few scopes that has ever shown me details on Jupiters moons -- the equatorial band on Io was very easy with this scope. And theres enough aperture for some nice views of nebulae and galaxies.
Mine did show considerable change in the collimation with elevation. It was pretty easy to see on star images at 500x -- the first Airy ring would become strongly unbalanced as the elevation changed. I could also see these effects on planet images at high power. For example, Jupiter at 45 degrees elevation would be very crisp, but Saturn overhead would show the effects of the extra coma. The problem can be managed in real time by re-collimating the scope on a nearby star prior to each planet observation.
A more permanant fix is to add some steel cables on diagonal lines between the trusses. This is pretty easy to do -- parts are about $40 and takes an hour or two. I did some lab measurements of the deflection using a laser, and it was something like 11 millimeters without the cables -- the upper cage was drooping by that amount as the scope went from zenith to horizon. With the cables it went down to about 1 mm.
Probably the collimation shift on the F/4.3 version would be smaller (shorter trusses) -- unless you are trying to squeeze the last ounce of performance from it, you might just not worry about it.
I also added four fans on the mirror to cool the scope more quickly. And some counter weights on the back to balance heavy eyepieces and camera equipment.
Also when I first got it, the secondary mirror was warped due to too much pillow batting in the holder shell. Images showed some astigmatism. But this was also easy to fix by taking out some of the batting. Its a fairly common problem.
Overall I would highly recommend this scope. Mine had some issues, but they were all easily fixed with some simple mods.
John, I have owned the f/4.55 version for six years. It is a wonderful scope. Superb Zambuto mirror. Easy to set up and take down, or you can just transport it in two pieces, as another poster has decribed. I have not found any cooldown problems. I do find the scope moves from the object when I remove a heavy eyepiece but I find it immediately by zeroing the Sky Commander readings. SC is very helpful in urban skies. I highly recommend this scope. Geoff Garehy on Yahoo Talking Telescopes group has one and loves it. Bill Meyers