I think the number of testimonials that (new users in particular) post on the forum shows that more people have a good experience against those that don't.
A rough estimation:
11221 forum users.
7 386 threads in the sections of the forum where problems are discussed.
If we speculate that 20% of PCLOS users register to the forum and that 10% of the questions here are about a serious problem then we have
11221*5 = 63 491 PCLOS users
7386/10 = 739 serious problems
63 491/739 = 86 happiness ratio
or 1,16% users with a serious problem
Now 3420 threads in the forum show as solved and this is 46% from the whole 7386 bunch of problem threads. So 1,16*0,46 = 0,53% of users exist with a serious problem unsolved.