Hi Michiel - I've used the Samyang for a few images now, and it's pretty impressive. It has a fair amount of distortion but it's very sharp and has nice micro-contrast. I haven't looked around for a lens profile yet, but I'd guess someone has built one to tame the barrel/mustache stuff. I've also heard that PTLens handles that pretty well but I haven't messed with that either. Even wide-open, it's quite good. It's manual focus only, of course, but that's fine by me. In terms of price/performance/value, it's kind of a no-brainer. I think they could charge 2-3x the price and it would still be a 'buy'.
Sorry to hear about your camera repair issues and hope that gets resolved soon.
-Doug