So simple yet so much scope. Rated 5 out of 5 stars

It basically means you can highlight any text, insert it into any url and open it directly on right click.
This means you can make custom right click searches on any site that has a regular url string when you search, which is most sites.

For example:
Search Twitter for "$"
https://twitter.com/#!/search/realtime/$

- For searching Twitter ("All", not "Top")

Because it's simple and logical you can even get creative. I use this:
Open "$"
$

- To simply open a new tab with the highlighted text in address bar, which I use to open plain text URLs.

It may be called "Dictionary"Search but it can do a lot more than that.

Rated 5 out of 5 stars

As far as I can tell, the only extension that gives you multiple context search engines without a sub-menu. Plus it works on editable text too.
The only extension I have that was worth forcing compatibility force Firefox 4 rather than finding an alternative. Would love an official update though.

This review is for a previous version of the add-on (4.0.1.1-signed). 

Hidden potential Rated 5 out of 5 stars

I basically use thing as a multifaceted replacement for the normal “search google…” right click context menu. I found that the easiest way to add any search under the sun, without mucking about deciphering urls yourself, is as follows:

Install “SearchWith*” (https://addons.mozilla.org/en-US/firefox/addon/2194), and in the config you will find an abundance of ready made search engines that you can copypaste into the 4 available within DictionarySearch. If you can’t find the search you need simply go to http://mycroft.mozdev.org/, install the search you want into firefox, then import it into searchwith and copypaste it into dictionarysearch.
Finally, uninstall or disable SeachWith and use “Menu Editor” (https://addons.mozilla.org/en-US/firefox/addon/710) to ditch the original context search.
This may seem a bit longwinded and backassward, but it works for me ;)

As for a review; this is the only addon I wish I could install twice. Seriously, the only thing that could make it better is having maybe 6 or 8 search options.

*Searchwith is a similar, and worthy, solution to right-click-searching but uses a nested menu to choose the search, which is why I prefer DictionarySearch. However, if you want lots (4+) search options it may be ideal for you.

This review is for a previous version of the add-on (3.0.0).