i bought the old ones
My 2c. I had the misfortune to get mugged, losing my old 8x42 ultravids in the process. This happened just as the HDs hit the shops, and just as retailers started offering remaining stocks of old ultravids at a significant discount. Wonderful, almost worth getting mugged. I had no hesitation. I contributed some of my own money to add to the insurance money, and bought a pair of old 7x42s (in green = more money off, a whole 200 pounds in fact, for something which makes no difference at all. You look through them, not at them.) and a pair of old 10x42s. I never even tried the HD, the old ones are so good that you can't possibly double that kind of quality, and I very nearly got 2 old ultravids for the price of 1 new HD model, and both the old ones have the better guarantee as far as I can make out. No contest, the well documented changes could not result in any improvement that would be worth paying that much more money for.
BTW I had never used 7x bins before, I now find myself using them about 70% of the time, which is roughly the split of time I spend in wooded areas vs open areas. They are excellent, I cannot recommend them enough.
I also use the 10x on holiday where I do not carry a scope, and I find that when you're using them day in day out, you become very accustomed to the narrower FOV, and can find birds easily. I find switching to them after having used the 7x more difficult.
I also find that the 10x sometimes have purple fringing when looking up at birds perched in trees with the sky for background. I don't see that in the 7x. Viewing in non-contrast situations is flawless in both. This was my experience with the 8x as well.
I don't use the objective covers - I found that when the bins were on my chest, no matter what angle I had them at, they tended to close themselves slightly as I was walking along, resulting in frustrating one-handed misses when carrying a tripod. I do use the rain guard though, which can also result in misses.
Anyway, as to old vs new, I respect people's opinions but I cannot believe that people would contemplate swapping if they already owned a pair. Or even if they didn't, the discounts should point them in the right direction. Of course another argument is that they should forget Leica altogether and go for the 8.5x42 ELs or Ziess FLs, but its a personal choice, and I love the leica image. I never tried the Zeiss, but I did pick up another birders ELs. I found them brilliant to hold, wonderfully sharp etc, what put me off was the length believe it or not. That extra cm or so made them feel too big. Plus they weren't on sale of course.