The two problems I've consistently experienced from cleaners are:
- lack of reliability
- lack of attention to detail/cleaning thoroughly
(I can also find some agencies just a bit too pushy and the hyperbole a bit unbelievable).
So, if I was to be specific, and not going into the complicated details of the type of property concerned, the problems would be:
Superficial cleaning which missed out areas such as skirting boards and specifically the part where the skirting board joins to the wall, which, left to my own devices, I hoover with a nozzle or clean with furniture polish, and use a toothbrush for (you have to be careful not to push any dirt into the wall). If the dust build up is really bad I actually repaint the whole skirting board, and that is not something a cleaner will do.
Or in the kitchen, failing to clean the bit between the bottom of the kitchen units and the floor, or in any gaps between the units. Missing the top of appliances is another one, or the outside of the drum of the washing machine. I've never met a cleaner who ever thought that cornicing required cleaning, but its a haven for dust. Mind you, that might be a blessing in disguise, as I wouldn't want harsh chemicals used on them.
Windows are another area of difficulty - myself, I would use something like a narrow wallpaper scraper to clean that bit between the glass and the mastic.
Or even just the corners of floor coverings and under beds - theres a difference between pushing a hoover around and actually using a nozzle to get into corners. Same goes for tiled bathrooms really.
I also hoover mattresses, duvets, pillows and sofa seat cushions.
The above is what I would describe as a deep clean, when you haven't had access to a property for some months, not one you do every week.
Since I can do it myself, I tend to notice when things aren't thoroughly cleaned because I know where to look. And I've had experiences of trying to persuade cleaners to do 5 or 6 hours well paid work, only for them to want to leave after say 4 hours, because they think they're finished. Of course, it is quite tiring cleaning properly. But whats the point in being a cleaner if you don't like cleaning or doing slightly dirty, unpleasant work?
I'm enjoying reading the comments above and the posters' attention to detail!