Trashbird et al., thanks for the comments so far.
I have had the Audubon 820s for a couple years now. I am very happy with them. The image quality is excellent and they have proved to be very sturdy even with the vulnerable ocular design all porros have. I always close down the focus on my porros before putting them away to avoid bumps bending the ocular arms. The Audubons can be turned down to rest the oculars firmly on the objective housing.
Trashbird, sounds like you are saying that the Audubons have the superior resolution and optical quality?
The main problem I would warn others about is the short eye relief on the Audubons. It is not really 17mm. If eye relief has ever been an issue, try these bins before you buy. I have always had to keep the eye cups retracted, even when not using my eyeglasses. Nevertheless, when I use my eye glasses, I find I lose only a small amount of the FOV and the image quality remains high. This is probably because I have always chosen close fitting frames and ultrathin lenses allowing my eyeball to get close to the bins.
For the rain guard, I bought the Zeiss model that fits their old 7x42s. It is the only one big enough to cover the massive Audubon ocular housings. Works well, keeping them dry. I have no plans to immerse my bins though, even if they claim the O-ring makes them waterproof. I have not had any fogging problems or water inside the bins despite being out in all kinds of weather.
Trashbird, sounds like there is no difference in the feel of the focus wheel. I find the Audubon's a little stiff, probably from the O-ring friction. The related factor is that the focus wheel turns 2 full times to complete its run. At first I found this annoying, but I am much more adept with it now and can focus fast. The payoff is that if I have even 2 seconds or more on the bird, I can fine focus amazingly sharp. I think this is a nice feature for any bin over 8 power where focal planes can get shallow. I admit though, it takes strong fingers and good pre-focusing skills to get the best speed out of these bins.
From the online descriptions, it seems the objective housings of the Ultralites are nitrogen purged. I do not believe the Audubon's are.
I am looking forward to trying the Ultralites. I was not too impressed with the previous incarnation, though I know they were considered top quality in the mid price range. I thought the view was not as sharp as some other Porros with full-size prisms costing less, such as some of the Nikon, Pentax and Minolta porros of the 90s. If you are right Trashbird, and they are using the same prisms and coatings from the old models, I dont think they will compare well with the Audubons.
If my bins "died," I think I would go out and get another pair of Audubons straight away. But, I am always on the look out for a better bin in this reasonable price range. Simply have not found one yet.
Welcoming any other comments from anyone who has tried these bins. Thanks.