From listening to the Best Match Webinar today, I don't think ebay really has a clear picture exactly how items are pulled up in searches, but they have an idea. I don't think the idea is bad necessarily, because the theory is to not punish anyone sect of sellers.
In reality, I don't think its working out like they hoped. I also don't think it was implemented well. It probably wasn't tested thoroughly enough either. And the most important part is that since ebay doesn't have a handle on it, they can't educate the sellers properly on how it works.
Its such a drastic change from how things were done in the past that in order to use it effectively, you need understand it... which isn't happening, not to mention its got glitches.
Basically, it was a helpful to gain insight into how the search works. Its worth checking out- may not a perfect system, but its what we are working in... or leaving... seller's choice.