I have tested a lot of searches (especially our competitors) and I personally feel we have one of the best based on PHP/MySQL.
However we are still improving it as we get feedback from users on it.

However if you want to search for just "cow" your users or you can use the "exact" search method (look in left menu and put a check in the exact box).
UPDATE: Also doing a search with " around the word will equal doing an exact search. Example searching cow and "cow" will give different results.

Then again I am not sure what version you have? You may not have the exact box, I think that came about in 4.0.8 or 4.0.9 (not sure off hand).

I can't speak to Ktools competitors, but the search is poor compared to my competitors. Granted, most of my competitors are custom built solutions. Still... the fact remains that when customers come to my site, the search is going to be noticeably inferior to pretty much any other site. That's not a deal breaker now because most of my traffic is walk in from Google, so I can let Google's search do the heavy lifting. But I also realize at some point (if my site continues to grow), I'm going to have to get it fixed or have a custom solution built.

that sounds good.  exact matches should still show up first - no matter what IMO

What about something like this (which I found in my effort to modify the search myself.. until I took a look at the search file and realized I was in over my head)

SELECT * from photos
WHERE searchterm like 'cow' 
union all
SELECT * from photos
WHERE searchterm LIKE '%cow%' and searchterm not like 'cow'

this will list exact matches first

http://stackoverflow.com/questions/1016804/how-to-sort-mysql-fulltext-search-results-by-relevancy

For me it seems like the best option is to have the ktools default search be as close to the most popular micro stock searches as possible for the best chance of our independent sites competing we must be able to give customers what they are used to. 

On the other micro stock sites and Google images search for example they do not have to use quotes or check a box to search for the word they type in, and if they use two search terms they can expect images with both of those terms to show up FIRST. This is the most important thing in my mind.  customers are not searching for single terms for the most part. As both a long time designer/buyer and a micro stock contributor/site owner I rarely if ever type in just one term, and when I type in a phrase I expect images that have all of the tags I've put in.

Weighted searches would be absolutely an amazing addition to this script BUT starting out with the basics to match our biggest competition (match all terms AND exact match by default) is essential!

Here is a new search file to try on your ktools photostore 4.1.1+
If you don't have 4.1.1 or greater this will not work.

Download search.zip, extract file to get search.php, copy search.php to root of your store files (you may want to rename your old search.php for backup).
You can now test the search and you should get items in relevant order. Example cow before coworker if searching for cow, or man before woman if searching for man. In those examples coworkers will not even show on the list since it is less than 70% match, same with woman since it is 60% match.

By default there is a cut off of 70% match, anything less than 70% will not show.
You can add this line to your assest/tweak.php file:
$config['searchRelevance'] = 70;               // Minimum amount of relevance from a search

Then adjust the 70 to what ever percentage you would like the cut off at.

any updates on this one?

is the new search.php as good as everyone expected?

Yup, the Standard search sucks, I mention that to the IT company working on my "CSS", they said there's an another way around (some sort of professional search script you can buy and install) but I'm not sure how much it'll cost! (probably more than the Script itself) anyway, I'll post "my solution" once we reach that part of our site.