I bought the X3 extender mainly for imaging solar system objects. So far I've only used it visually with my Skywatcher 200P Dobsonian. Views of the Moon terminator using the extender in combination with BST 25 mm and 15 mm eyepieces were crisp across the whole field of view. My various Barlows tend to give a softer appearance even under good conditions. I look forward to having a go at imaging with the focal extender.

Using this with 20mm/100deg eyepiece. Resulting views are crisp and minimal loss of brightness.

It looks fantastic, it feels good to the touch and it is quite heavy., but in a good way. Looking forward to my first field test.

Very little opportunity to test out ES 2x Focal Extender due to terrible weather, however a few thoughts and highlights.
1) It is heavy! Needs considering for some equipment and potential uses (e.g. on a Dob-mounted Newtonian with an already heavy eyepiece).
2) Well constructed. It looks and feels solid. A real upgrade from my existing "with scope" 2x Barlow. (Although to be fair the Sky Watcher 2x Barlow is not bad.)
3) Visual observations of moon paired with Altair 152mm refractor and X-CEL XL 12mm eyepiece (+ adaptor) - brilliant! One of those "works perfectly without dramas" moments. Suspect this combo will become a "go to" when seeing allows.
4) EAA with Atik Horizon OSC. Worked well to visualise small, bright planetary nebula - NGC 2392 in Gemini.