There are various reasons why transactions are not seen or propagated and of course it is a process of gradual improvement to eliminate these. We have various support items on multibit.org to help people when they encounter this problem.
"More often than not" is over 50% of all cases which is _slightly_ hyperbolic.
There were a third of a million downloads of MultiBit in November, basically being supported for free by Gary and I in our spare time.
Your support articles helping users when they encounter this issue are of course helpful and appreciated.