I have two panniers and they appear to be fine, used mainly for short trips and shopping etc. including on canal paths and rough tracks.
Fitting on a standard rack no problems, secure and easy to use, these bags are considerably cheaper than similar rivals and, unless on a serious expedition, I cannot see a reason for most people needing to spend more money. I haven't had any problems with lack of waterproofing and I would suggest that for the price difference, unless this is a major concern, the use of bin bags or similar as liners would suffice as insurance.
The bag has a useful, detachable, shoulder strap making it easy to carry around, especially when shopping etc and a mesh inner pocket for easy access to valuables. At 23 litres the bag is about the size of a small walking "day sac".Two together would be enough for a weekend or slightly longer. For the price, very good. Recommended