It is ideal for office store rooms and domestic storage. Especially in potentially damp areas (not that what's on those shelves may be suitable for damp areas).
The 50 kg UDL equates to 12.5 kg per shelf corner. That is a better gauge than "Uniformly Distributed" which in my experience is difficult to achieve.
The shelves will, and inevitably do, sag in the middle. Not much, but it's better to keep them out of sight.
I put a block of wood under the centre of the bottom shelf for extra support, and then put heavy stuff on it (perhaps too heavy). I think there is room in the pack for the manufacturers to put a plastic box shaped block in there for that purpose.
Of the 27 shelving units received, there were six broken shelves. Analysis showed that they were either the first or last out of a pack.. The only thing that could account for them, is that they were broken during delivery by being plonked down, end on, onto a hard surface. I have recommended that a sticker be added indicating "handle with care, this way up" to ensure these units are delivered horizontally.
I've experienced a fire hazard with the PP5s, that potentially applies to all shelving and racking used under halogen down-lighters. I bought PP5s to make use of the vertical space in a storage area filled with cardboard boxes full of stuff, that could not be stacked one on top of another. During assembly, I emptied the contents onto those shelves and put the empty boxes on top of a pair of shelving units. That created space for the next shelving unit. The collapsed boxes mounted up. All was OK until I turned the lights on. Then there was a smell of hot cardboard, followed by charring. I removed the top box and saw a glowing ring the same size of a down-lighter. Moving that box fanned the glow into flames. All 50W halogen down-lighters have now been replaced with 15W LED versions. Probably worth doing anyway for financial reasons.