Last night I went ahead with the Mac OS X upgrade to Snow Leopard. The upgrade worked like a charm except I had to upgrade two software to latest versions (Zoc and iStats Menu). Other than that I have not found any major issue.
Since Apple claimed that the upgrade should free up 7GB disk space, I kept a note of the disk usage before the upgrade and once the upgrade completed I had gained 15GB disk space!!!
And to top it all now Urdu Nastaleeq font works great in Safari browser!!! This was one of my wish that Mac could support Unicode OpenType Nastaleeq font in the browser. It worked before in TextEdit in Leopard but now it works in Safari as well and we can read Urdu articles and websites in beautiful Urdu font.