I've noticed that if you are a fast enough typist, the search in the menu can miss the second key.
Examining things carefully, it appears to have to do with people (like me) that tend to depress the next key before lifting the prior one.
The search seems to react only to keyup events, but the input box for searching needs to see the keydown in order to pay attention to the keyup.
So the timeline goes like this (example of searching for "firefox"):
- f down
- i down
- f up
- search box shows up, f inserted
- i up, search box ignores this event as it didn't see the i down event
The end result is now that the search box is open, has "f" in it, and then it gets "refox", making for a failed search for "frefox".
This is a known issue. For bug reports with the Platform pre-releases, check out the Platform 'Next' Pre-Release Bug Reports thread.
Further testing clarifies that this is the case.
With the search box opening on keyup, and further input being on keydown, the following procedure causes the second character to be left off:
This can be replicated at slow speeds, it is just not the normal way to type, so it is only usually noticeable when typing at fast speeds.
EDIT 2: Removed the bit where I contradicted both Cheetah and myself and made it sound like I figured this issue out all by myself.