Thanks for the quick reply Rated 5 out of 5 stars

Thanks for addressing all the issues I had raised Mingyi. I am satisfied with your explanation about:
- Not adding more search engines to Fastest search
- Not allowing a search engine keyword of more than 3 characters

I am happy that in future versions you have agreed to see whether the limitation of numerals in the search engine shortcuts can be removed. Also, it is great that you are going to remove the bug that causes smart search to not be disallowed easily.

w.r.t. your explanation about the settings interface, I myself am not bothered by it much, but I think that the average user does not take time to stop, read all your instructions in the ? buttons, and then configure the addon. I think it would be better if you make the process of adjusting settings a bit easier. You should probably consider allowing people to choose between 1.All settings enabled 2.All settings disabled 3. Medium settings 4.Most important features enabled and so on, in one separate window. Probably in this new window you could have check boxes to allow people to quickly enable or disable features more quickly. For example, it could contain a checkbox to enable/disable Instant suggestions, Smart search, Image save, Preview, Autocopy, Text search, Preview
and so on all in one window. If one wants to fine tune the settings for each of them separately, then he has the choice of going to the specific window of that feature and adjust them in more detail.

I love your addon, and I would have awarded you 4.5 stars if Mozilla would allow me to. I have corrected the 4 stars and awarded you 5 stars now, But please
- Allow us to disable the smart search easily(as you said you would do it in a future version)
Or
- Allow us to add more than 7 search engines to smart search

Your addon would deserve 6 stars if you did both of them together.

This review is for a previous version of the add-on (2.14).  This user has other reviews of this add-on.

Thanks for your update as well!

Now:
1. Removing the limit of numbers in engine shortcuts: UPDATE: it's done. Can you send me an email so I can mail the new version to you and you can test it out? I want to test it out a bit further before releasing it.
2. I agree. Allowing users to quick-sets would be better - it's partially done with the Instant/Suggestion/Image Save/Autocoopy/Smart Search (via method below, although not a checkbox) all needing just one check/character change, but it is not all in one place or straight forward. I'll think about it.
3. Disable Smart Searchbox is already easy (just set the "Hide Smart Searchbox after _ seconds" to 0). It's the preferred way (this way you preserve the engines, which would be useful when using 'shift' key to bring it up again), but I already fixed the bug. UPDATE: as above, contact me using 'support email' on addon page, I can send you the update.
4. More engines in Smart Searchbox. I'll see if I can make it arbitrarily big with a certain limit. It'll be a little tricky and could take a bit time/planning.

BTW I seriously recommend watching the 8-minute intro video I linked in the 'About this addon' for FS. You'll truly find the textbox in the Smart Searchbox unique and quite useful. The auto-guess engine using the default or customized text-recognition rules is also unique and quite helpful.

I'll update this reply when I release a new version that addresses some of these things.