I have. The 30 mm UFF is about 4 ounces lighter, more compact and has quite a bit more eye relief. It's very sharp across the field and the entire field s easily seen. It's a fine eyepiece.
The 28 mm UWA is quite a different eyepiece. It's still light compared to the 31 mm Nagler but it's somewhat short on eye relief, still very usable. The upper part of the torpedo body is a bit larger than the others, 2.2" instead of 1.9"-2". It works for my narrow eye sockets but just barely.
Optically, it has the immersiveness of the 31 mm Nagler. I put it in the focuser of the NP-101 or an F/4.4 Dob with a Paracorr and I feel like I'm getting the full field, I'm not wanting anything more.
I measured the AFoV of the 30 mm UFF, the 31 mm Nagler and the 28 mm UWA, ~70°, 82.1° and 84°.
The 28 mm UWA is a worthy competitor to the 31 mm Nagler, the true field is only 3% narrower. The 30 mm UFF is a different sort of eyepiece, certainly a very good eyepiece but with more emphasis on the compactness and less on that ultimate wide field feel.
The UWA also feels like it has better transmission with narrowband filters. The Catspaw nebula with an O-lll filter seems more "lively." The UFF shows the basics but there's more bits and pieces with the UWA and the Nagler.
I'm keeping them both..
Jon
Excellent; thank you!