It has been know that a port of Firefox for Android, as known as “Fennec” exist..
It is 4xMB in size (I finally come to this day that my N1 report it is FULL on storage, so I did empty some unused applications.)
Results were quite disappointed, speed was slow on my N1, rendering was messy, and it hangs so many times in my 5 minutes testing period.
I understand it is the first public beta, uninstalled by now, and wish all the best and hope it gets better and better in time.
If you are still interested to try it out yourself, head to:
http://www.mozilla.com/en-US/m/beta