Agree about the Samyang. Originally, I did get it principally for astro, but I've found I've used it more often during daylight hours - whenever there's an interesting sky. It's certainly one of the genuine bargains in the photography world.
I have four MF lenses – three from Canon (17+24 TS-E and the MP-E 65), and the Samyang 14/2.8 (which I use for astro, and it's great).
So far, I've avoided being bitten by the Zeiss lens bug. Well...for my personal photography, at any rate. I've bought ~$2MM in Zeiss research equipment (not my money, of course), of which close to ~$200K was for 'lenses' (microscope objectives).