The answer is yes. 

You can do it with anything from cinema tickets to cars. Examples of group buying discounts. 

Cinematicket. Normal price at our local cinema = 70 (+10 if the movie is 3D) Group price 35. The cool thing about the cinema tickets is that you buy them, get a text message with a code, when you want to go to the cinema you go and tell them the code, so you need not decide on time when you group buy. (although the tickets expire after some weeks, and then it is wasted money)

Restaurants. Zhuhai has a western buffet that is pretty good. The normal price is just shy of 200rmb for dinner. The group price is half of normal price. 

As I don't do any group shopping myself but leave that to my lovely wife, I am not entirely sure about where to do it, but I know that for both cinema tickets and the aforementioned buffet, the group buying is done on taobao. 

My girlfriend uses tuan800.com

Apparently it's the best one out there. It regroups all the group buying websites into one. It's sort of like a search engine for group buying.

^ Wow, your gf got a good find.  I frequent Meituan and Dianping, and occasionally Lashou and others, but putting them all in one place is pretty awesome, and I like how easy the search options are to use!

Anyway, as for the question, group buying is well worth it.  For movie tickets, amusement parks and buffet's, you'd be crazy to pay full price, as the group deals are always half the cost if you walked in.  I use it to buy the little things like milk tea or a snack, and try new restaurants around the city (and save money when I do).  If you have Android or an iPhone ,the Meituan app is great for finding shops nearby with a deal.

Most reputable is definitely Meituan and Dianping.  They get the best deals, and I've never had a problem getting a refund on something.  Dianping is the Yelp of China, so you can view pictures and reviews of any restaurant.  Meituan has group views only, but I like their selection of deals for food or coffee the most.