My research in a few other places indicated that it isn't such a bad thing as it initially sounds like.
Video from 10gen talking about the global lock : http://www.youtube.com/watch?v=PIWVFUtBV1Q ( Skip to 55:00 for the global lock question )
Current version of mongodb : 2.4 -- Global lock removal happened in 2.2 Details: http://blog.serverdensity.com/goodbye-global-lock-mongodb-2-0-vs-2-2/
From watching a couple of other videos on it, the following statements sum up my current understanding of the issue :
"10gen rep : The global lock is something we are very serious about. The server wide lock is gone, now it is a database level lock and in the future we plan to make this to collection level.. "
"If the record you are trying to update is in the RAM, you will not notice the update because its so fast. It sounds really scary but, you shouldn't face too many issues because of this"