Rated 4 out of 5 stars

Excellent add-on, but when you have a lot of contacts as I do (over 3000), when I start typing a contact, the MRC compose, instead of waiting for me to pause typing, immediately starts to look up contacts, and then when I type the next letter it starts again with the lookup. So it is very very slow to catch up with my typing.
There should be a short delay (maybe 400mS) to allow a user to type several characters before it starts to look up the address book.

This review is for a previous version of the add-on (1.8.3). 

Thank you for your interest in MRC Compose !

I took care of large number of contacts, not as you suggested by a timeout, but in a simpler way : just a number of characters before starting search.
You can change it in the preference panel, second tab, option "Start search after nb characters". Set it to 2 or 3 to eliminate most of yours slowdowns.
Hope it'll help you.

Cheers,
Michel