Some more reports:
After successfully creating a new compression ring to hold the WO Zoom in place, I did some extensive seawatching this weekend. My impression was very positive -- this is an excellent, sharp eyepiece. It doesn't give the wide, immersive feel of my XL 14, but was very comfortable when viewing at the wide end and easy to zoom in.
I mentioned before that the zoom action felt a little loose to me, at least looser than some other zooms I've tried. I actually really like this now -- while seawatching, it is really nice to be able to scan at the wide end and then lightly zoom with one finger while tracking a bird. Other zooms require you to grab firmly and rotate, which shakes the scope more. The WO Zoom is definitely still smooth, it just happens to require very little pressure to move the zoom ring.
I didn't do any A/B tests with the XL 14, that will come this week. I will say that the WO Zoom felt crisp and sharp, and very neutral in terms of color cast. Eye placement is very forgiving, more so than the XL. This is a comfortable eyepiece to use, I find it to be MUCH more comfortable than any other zoom I'm tried on this scope (though not as nice as the Zeiss/Swaro zooms or the new Kowa). Absolutely blows away the Pentax zoom I tried briefly a couple of weeks ago, which was massive, stiff to zoom, and not very fun to look through.
I tested edge sharpness by focusing on a distant bird or sign and moving the scope around -- sharpness stayed strong all the way to about 20% from the edge, where there is a little "halo" or "coma" effect at the very outer edge.
I did find that the "sweet spot" of the PF-65/WO Zoom combination seems to be from 20mm to 10mm (20x to 40x magnification). The most comfortable area for scanning/viewing -- the "sweet spot" of the "sweet spot" so to speak -- was around 16mm to 13mm (25x to 30x). This is consistent with my past eyepiece experience -- the Pentax PF-65mm is happiest right at 25x to 30x for overall use.
I actually found that 22.5 is too wide -- I could see the outline of the "notch" in the focuser tube barrel when pulled all the way out! A tiny tweak of the zoom to 20mm or so cured that, but I found I never used the zoom at the widest setting.
I would also do tests where I would zoom all the way to 7.5mm (max zoom) on a bird, and then back it out slowly until I felt the image was comfortable and crisp. Then, I would look and see what zoom setting I ended up at -- it was always a little bit to the right of the "12" on the barrel, meaning about 10mm or so (i.e. 35x to 40x).
I did a similar test starting at the wide end, and then slowly zooming until I thought that I was losing brightness/clarity. Here I usually ended up at the "12" or a little bit to the left (i.e. 30x to 35x). Again, this seems to confirm my overall experience that it's when you approach 40x and above that things start to break down a bit.
Overall I found little reduction in clarity/brightness between 20x and 40x, but above 40x you start to get into the problems of magnifying air distortion etc. (this occurs with any scope at distance I've found). Anything above 40x is too much power for panning/movement because it magnifies the vibrations so much.
However, when the scope was held still I could effectively zoom all the way to 7.5 to get full power. I had a nice little test where I was looking for a distant female Black Scoter in with some Surf Scoters, and was alongside a friend using a new Swaro 80mm HD. When we found the bird, he zoomed all the way in to 60x and I was able to compare the big Swaro at 60x to my little Pentax at 52x.
While the 80mm Swaro was obviously a little bit brighter and crisper looking at this little duck about 1 mile away, the difference was not huge. A tiny nudge back from 7.5mm (bumping magnification down to the high 40's from 52x) made a big difference in terms of sharpness and clarity -- 52x is definitely pushing the optical limits a bit. (Not that this scope can't handle the resolution -- if you zoom to 52x on an object that is only 25 feet away, it is perfectly clear. It's just that at this magnification you are really going to have trouble seeing through all the atmosphere between you and a distant bird.)
Tests like these make me happy and allay any "buyers remorse" or "scope envy" I may get. Again, the Swaro was a little better, but certainly not $2000+ better versus the $650 or so I spent on my PF-65ED + WO Zoom combo. If you have the money, and need a dedicated scope for sea-watching or real demanding conditions, the big guns Zeiss 85mm, Leica 78mm, or Swaro 80mm are still better to extract that last drop of brightness and resolution. But again, the difference is not THAT big at all. Honestly, I might take the Nikon 82ED with it's ability to zoom to 75x over any of them, having seen first-hand the difference it can make on a friend's scope looking at a very distant bird.
The only scope I've seen which really made me go "WOW" was the new Kowa 883. Wow. A birding pal just got one and it is unbelievable, but then again it's close to $3000 when all is said and done...