I realize supermarkets aren't venues that are usually reviewed (I mean, who checks out ratings for a hypermarket before shopping there?!) but I had such a stellar experience with this branch that I had to tell the world about it!
We've been loyal customers with Union Co-operative for almost 20 years now, working our way through branches depending on the area of Dubai we were living in. For Mirdif residents, this (relatively) new branch has been a blessing, and it is often much easier to just head on down here rather than wade through crowds to get to Carrefour in the nearby City Centre.
Union Co-op caters predominantly to an Emirati clientele, with special loyalty programs tailored purely for locals (and those too only Dubai ones - Abu Dhabi residents not welcome!). You still find all kinds of people doing their groceries at this location and it is never too crowded. Prices are consistent with other branches around town.
The ladies at the cash counters are VERY friendly and if you can spare them a smile, they'll be really nice and speed you through checkout while making small talk. The only problem I had were the bag-boys :( I understand that these guys are stressed out, living mainly off tips and working 12 hour days. I sympathize with them. However, here's the problem: wearing jeans and a t-shirt? Unload your goods onto the cashier conveyer yourself. Look Arab? They will unload your trolleys for you on top of everything else they already do.
I understand that this is not the norm - most places don't offer that service at all! My complaint was this - do it for everyone or do it for no one. I raised this 'complaint' in a very friendly manner via a suggestion form at the information counter and left (after tipping the nice gentleman helping us, of course) thinking it wouldn't really make any difference. Next day, I got a call from a very helpful Customer Service Supervisor promising to look into it! That was the biggest surprise - GOOD customer service in Dubai!