I'm not sure their reservation system actually does anything.
For various reasons I needed an extra hard drive caddy.. could have got it next day from amazon but this couldn't wait, so I did a 'reserve' on the PC World website and set off up there... so arrived maybe half an hour later. It's a £10 fairly common item.. should be easy, right?
They had the reservation on their system, sure, but it took the staff completely by surprise that anyone would actually want to pick one up - it took multiple staff hunting around the back of the store.. I was stood at the till for another half an hour before they turned up with the caddy. I would have walked out, but needed the damned thing.
In my head a reservation would mean that a little thing would pop up and a minion would go to the right place in the stock room (catalogued.. if your'e searching for stock you're doing it wrong) and put it behind the till.. 2-3 minutes tops. That's clearly not what happens..