If we could vote negatives, I'd vote against the 2.8 asph Elmarit. (1) IMO it's too contrasty and compromises some shadows or highlights in bright sun. I got one new with M8 but soon exchanged for a Summicron. (2) I don't think the Elmarit is preferable to the less expensive Biogon. I liked the light weight of the Zeiss on my backup camera and am sometimes sorry I'd ever 'moved up' to the bigger & clumsier Summicron. As Pieter said, "Is it worth the price? Don't think so, but in five years I ... have forgotten how much I paid for it."
I also have the original (1.9) Ultron, and find that it renders a lot like my old 8-element (v. 1) Elmarit, but resolves much better at 2.8. It's my 'beater,' to use around sand, thugs, and children. The v1 Elmarits are costly collectors' items now, and my used Ultron was less than $500 (with hood & coded Millich adapter). IMO the 1.9 Ultron is the 28mm user's bargain.