I can't speak for the other versions (Yugo, Russki, etc.) of the SKS. I own a Chinese variant and the length of pull is just comical in OEM form if you are over 5'4". I'm 6'3" and the Tapco stock was just the ticket.
They are pretty well made and they look pretty good once it's all together. Fair warning, the gas tube cover is a bit of a pain to fit. I had to drill out the pin, drifting it wasn't happening. Also plan on taking your time and filing it to fit. Worth noting, I'm sure someone with more skill than me can get the wooden gas tube cover off in serviceable condition. I tried and failed. If keeping it (the old stock) on hand matters, you might wish to have the gas tube cover portion done by someone with actual skills.
Weight? You will save some, not so much as to be a big deal.
Length? As far as actual use, the adjustable stock is a godsend. Compressed, the Tapco is noticeably shorter. How much? Don't really know.
One thing I noticed is that for some reason, the recoil seemed more unpleasant. I suspect that the less rounded design of the Tapco buttplate is the culprit. It's not a big deal, but it could be a problem for someone that is extremely recoil sensitive.
IMHO, it was a big improvement. I wish I'd done it sooner. YMMV.