Naveen, it depends on one's interest. In the past 3 years, you might have realized what suits you and what you are interested in - A technical or A Managerial career path.
If you want to be a pure techie (say, Architect) then MBA doesn't give you any added advantage, but if you want to get into management then MBA is something good to have.
If you plan to go for an MS, then even after doing your MS you still have both techincal as well as managerial career paths open. But, I personally believe, for managers MBA adds greater value than MS.
AFAIK, part time degrees aren't given much importance (in India) so if you are really serious, then give a thought on a full time degree.
Finally, one thing - whichever you choose, it must be your option and not because others suggested it

[ July 31, 2007: Message edited by: Srikanth Basavaraju ]