I have problems with search settings. I use 'Title' in the options page to set the sort order but the result is not in any visible order. I'm using 1.4.7 but it appears to be the same with 1.4.8 on my test system. If I change it to 'filename' it is more what I expect but the title is what really counts for me. And I tried it with some of the standard themes where the result is the same. Check on http://www.paledog.de , use one of the Tags and see that it does not order by the displayed title.
Content, Description, Tags and Title are enabled. I have pictures where only the title differs but the rest is the same. Shouldn't they be displayed side by side? And if search displays by weight why is 'Filename' in 'Sort Images by' working better? I have the feeling that 'Title' is somehow getting ignored.
If I click on "mercedes-benz" on the tag clound on the left I do get a lot of entries for that. What is wrong with that actually?
The difference between title and filename is in any case that titles are multilingual (although on a fixed term like Mercedes Benz that doesn't matter).
I cannot exclude that there is a bug in the search engine stuff but I cannot answer without further investigation as I didn't code all that stuff originally. Sadly I am lacking a bit the time to do such an investigation right now. Please open a ticket so it doesn't get lost.