You're partly right, satisfied users are much less likely to write about their experience than dissatisfied users, it's the nature of things. it's better to rely on industry figures and statistics, return rates, etc, than user reviews anyway, although user reviews can be helpful they're not always accurate.
As for whether you should be able to feel the difference - no, the motherboard hardly ever has an impact on performance unless it's broken in some way or uses an inferior chipset. The difference is more in terms of customer support, features, longevity and reliability.