I use a Star Adventurer, I used to also own an iOptron Skytracker, but I sold it since I basically stopped using it after I got the SA and my Sirius mounts. I mostly now use the SA for my wide angle nightscape stuff and shots up to 135mm (using my Samyang 135mm f2 lens). I have used the SA and its ST4 guide port to do long focal length shots with my 150-600mm Tamron and one-axis guiding, best I was able to do were 4 minute exposures at 400mm with that setup, guide error was around 2-3" RMS if I remember correctly.
The pros are that it's small and lightweight so it can be setup, even with the counterweight, and then broken down and packed up. I can setup/take down the whole thing in about 15 minutes now. It has a good polar scope with decent optics and a nice reticule that makes polar aligning pretty easy. If you get the astro package you also get the Dec bracket which has a gap that allows you to mount your equipment and still use the polar scope, the photo package just includes an adapter which mounts over the polar scope and blocks it. It has several guide speeds to choose from, including solar, lunar, and up to 12x sidereal and it has fine tune controls for both the RA and Dec axis which helps with framing your object of interest. Obviously the ST4 port is an advantage for doing some limited one-axis guiding if you want, I had no problems setting up the mount to do it. Everything is well made and solid, you'll get the best results with a decent tripod (with, say, a 20+ pound payload capacity).
The cons are that the polar alignment instructions (and the manual in general) are all but useless and the first thing you should do when you get it is throw the polar scope illuminator in the trash, it is completely useless. The RA clutch can be a little finicky to learn how to loosen and tighten, if you get too aggressive with it (over-tightening and then trying to loosen after you've got everything mounted up) you will definitely screw up your polar alignment. You have to buy the wedge separately and you'll definitely want that and the azimuth adjust range isn't very large.
Overall for ~$400 for everything (including the wedge and counterweight setup) I don't think it can be beat in terms of the lightweight portable tracking mounts. Here are some shots I've taken with it and various focal length lenses:
Alone Atop Lone Rock by Eric, on Flickr
Pleiades Dust by Eric, on Flickr
Orion Mosaic by Eric, on Flickr
Horsehead and Flame Nebula by Eric, on Flickr