Rated 4 out of 5 stars
Has great potential, but I find a few bugs when using it on Ubuntu (Linux). The biggest problem is that right clicking on the query box does not bring up the option to add a search engine -- the usual copy, cut and past menu pops up instead. (It would be nice if a icon would appear in the query box to add the search engine) I have also tried v1.41 but there is no icon in the bottom right corner of firefox -- and the option to add a search engine still does not work (even with the "test" query).
EDIT: Not sure what went wrong with my original install, but I removed Fastest Search then reinstalled the current version (1.35) from Mosilla site... and I have the icon showing and I can create a Fastest Search. Now the only problem is that I can't get the icon to save using the demostration that I've followed in the third video.
EDIT: Much improved since version 1.35. Version1.51 works well on Linux (Ubuntu) and Mingyi Liu has added a number of features and fixed many bugs. Well done!
Edit: I'm glad that you worked out adding custom engine. The v1.50 also solves the icon issue you're seeing (which was due to your removing searchbar, 'causing Fastest Search to throw an error. v1.50 no longer throws error and fall back to urlbar whenever searchbar is not found).
v1.50 also solves the other issue you faced: it now makes adding Fastest Search engine for the small number of sites without forms much easier. Just type 'TESTKEY' in the query textbox of the site and search for it. Once result page is fully displayed, click on 'Fastest Search' icon, then select 'Add Engine for Current Page'. Favicon, query URL etc. are all filled. Just give a category and shortcut and you're done.