Speaking from the opposite angle, as someone who has an apartment that we rent out privately, and started off advertising on holidaylettings (but have no need now), I think its a gamble for both parties.
I have to say that I always have a bit of an 'email chat' with anyone who shows interest in our apartment, just to make sure that what we have to offer is what they are looking for.
The last thing we want is for somone to not enjoy their holiday because they didn't choose a place that suits them. The other danger is that you rent it to someone who doesn't look after it - fortunately this has only happened once in the six years we have been renting it out.
On the plus side for holidaymakers is the fact that as someone else said, you often get many extras if it's used by the owners themselves, and you usually get a very personal service tailored to your requirements. You can also ask almost unlimitless questions and get the right answers!
We have also now booked a few places independantly from owners, and so far it has worked very well for us.