A lot of the brands they sell are almost Aliexpress-grade knock offs of known brands - they'll mimic the branding and packaging of a known brand almost to the point of being an exact copy with a slightly different name. The quality of these knockoffs is also pretty questionable in my experience, but some are actually comparable to the real thing.
Another minor complaint - the staff don't pack your bags like every other supermarket, but they also don't have self service checkouts so you get the worst of both worlds and none of the benefit. Every store near me is chronically understaffed as well so actually checking out can take upwards of 10 minutes even during off-peak hours.
Overall though it's not much cheaper and the whole thing kind of feels a bit grubby, don't really see any reason to shop there.