Well, I got the elmarit, however, I can't do a side by side, as I had to trade the Avenon to be able to afford the elmarit! However, I did do some shots in the shop, and was able to look at them at 100%, so I'll just have to share what I saw at the time.
They had two copies of the elmarit, one was 326xxxx and the other was 321xxxx, which I think dates them both to '83, so they're quite early examples.
The first one I tried was definitely not focusing exactly at infinity, but nevertheless was more contrasty and sharper wide open where it was in focus. The difference at 5.6 was very slight. The biggest difference is that the Avenon shows much more chromatic aberration at the edges, especially at the larger apertures.
The second one I tried (the older of the two) was altogether a better performer than the Avenon at 2.8 but again there wasn't a lot of difference at 5.6. The difference wide open was enough to persuade me to fork out for the Leitz lens. It's hard to put a finger on it, but it just looked better at larger apertures. For example, chrome chairs outside a cafe across the street looked crisp in the elmarit, while they had a sort of soft halo effect with the Avenon. The differences were really only visible at the edges... in the centre the Avenon looked every bit as sharp as the elmarit.
So, sorry no direct comparisons, but I will be posting some pix with the new lens, and I'm looking forward to seeing what the lens can deliver using RAW.
By the way, given the price drop on trade in, getting this lens has ended up costing me as much as a good used 21/2.8 Asph! Such is life. Moral: buy the best lens straight off, even if you have to mortgage the wife!
Phil