I have noticed the combis which have "instant" hot water (i.e. the ones that keep a small store of a few litres pre tempered) work better in this respect. As the demand falls below the burner minimum it shuts off, and they keep supplying hot water from the store. As the store cools they relight the burner to temper the store. So you can have a more or less continuous trickle of hot water if you want. The temperature fluctuates a bit, but not enough to end up being cold or needing you to turn the tap on more.
I have noticed there have been a number of threads recently concerning the "fringe" behaviours of combi boilers (i.e. non obvious pros and cons). It would be quite handy to compile a table of models that exhibit these issues since it is the sort of information that is difficult to get from data sheets.
For example: how much hot water do you need to demand to get the boiler to switch into HW mode? Some I have used are pretty insensitive such that you need to turn the tap on pretty hard for the boiler to notice. Some are daft to the other extreme (like my mum's Myson) where even a dripping tap will leave it stuck in HW mode with no heating.
What happens at minimum flow and below? What is the temperature delivery profile like (i.e. is it one that accumulates a small pre charge of scalding water)? How good/bad is the fan noise? I am sure there are plenty of other examples.