Perhaps we've been lucky, but we've never had any major problems with landlords here (so far, at any rate). Our approach has always been to treat the property as if it were our own and look after it very well, as well as paying the rent by standing order towards the end of the month before it's actually due, making sure that aircon servicing and other requirements are carried out consistently, etc. Alongside that, I generally take care of repairs myself if I am able to, without involving the landlord or their agent unless it's a major issue that needs their involvement. Above all, I'll always try to avoid getting into a pi$$ing contest over a relatively trivial matter. That seems to have paid off for us over various rentals.
I know, from reading some of the stories on here, that there are bad landlords out there, but there are also bad tenants, who just bugger off without meeting their obligations. This I believe can make even a 'good' landlord very wary, which may have an impact on later tenants who may have nothing but good intentions.
The one area of difficulty we've had is getting back the deposit at the end of the tenancy. As the deposit is held by the landlord, it sometimes feels like they regard it as 'their' money, which you have to convince them to give to you. Obviously there has to be an equitable system whereby damages and other costs are accounted for, but even after that has been done, we've had problems in getting landlords to pony up the deposit (or balance thereof). This has happened not only with a private landlord, but also with NTUC Income, who were the owners of one of the previous places we lived in.
As landlords in the UK, our experience with the tenancy deposit protection scheme there has (so far) been good. JR8 may have views on this, but IMO it's a good idea that the deposit is held in a separate escrow account, and not by the landlord. I think it would be a good step forward if a similar scheme could be introduced here. But at the end of the day, I'm just a 'guest' in this country so what I think doesn't really matter to the gahmen.