I have the Samyang 24TS and the 14mm, certainly the 24TS is great value in the bigger scheme of things. It is known to be soft wide open , but at realistic apertures it's sharp, and as it has a manual aperture ring it's a great add on for my m43 where I get the benefit of articulated screen/focus peaking and double the focal length. It's easy to compare the Canon version as 'just twice' the price, but we're not talking the difference between £200 and £400.....£900 and £1800 left me with enough to buy the 14mm and £600 in change.
Just shows that creative photography lives between the ears, not in the next to be released gear upgrade.
Seems like many on this site will pay thousands to buy the latest gear to photograph their dog/cat/children (in that order). Within months they're pleading with the manufacturer to release the next better version.
Once the megapixel count became sufficient and higher iso became clean enough I really stopped looking to buy (I use a 1DsII and a 5D) and really started to use the gear I had. The best value for money gear I've bought is a pair of really good walking boots and waterproof clothing, this allows me to get out there and take images when most are aiming at the dog.