I have a pug and I am a vet.
My pug is treated like a 'proper dog', is kept VERY slim and fit enough to do long walks with my other (very athletic) dogs. He is very friendly with people and hilarious to be around.
The downside: He is very vocal and very opinionated. I got him as a young rescue because his previous owner couldn't cope with him. Housetraining was a nightmare and we still get the odd accident. Other dogs are often wary of him as I think they find it hard to read his body language (wide mouth, wide eyes, short curled tail). His breathing has been assessed and he is pretty good (for a pug) but has had surgery on his eyes to try to reduce the risk of him developing corneal ulcers. He also has a congenital spinal malformation that he copes well with at present but is likely to ultimately shorten his life expectancy. Anyone taking a pug on should be prepared to pay for airway and eyelid surgery as a very minimum. They are also very prone to atopic dermatitis, mast cell tumours, syringomyelia, etc, etc the list could go on.
Whoever said that Pugs should be allowed to die out is nuts. They have been in Europe since the 16th Century and in China for a whole lot longer than that. If you look at old paintings though, they were taller, sportier dogs with longer muzzles and less bulging eyes. Far too many pug pups have been registered with the KC in the past few years, and in my opinion, the problem starts with the perception of what a pug should be. The potato-shaped blobs with bulging eyes and no nose are not really what we should be encouraging, either by buying the pups or placing them in the show ring.
If you want a pug look for something with a longer muzzle and open nostrils. Avoid if you can see a lot of the white of the eye. Once punters act with their wallet (and the bloody breed standard is modernised), hopefully things will change and welfare will improve.
(Mine is castrated btw!)