Hi Dean,
Thanks a lot for replying back,really appreciate for the detailed review there.
Well Dean to be very honest I'm not really keen in switching to Aperture that's the reason I'm here in this forum cause I wanted to have Lightroom up n running on my iMac as I didn't knew the process as I'm new to the Mac world :).I have never used Aperture before but so far whatever inputs I have got points out that it's not bad at all and comes at par with LR,so its not a bad deal to try that for sometime and especially when u can get it as a gift from Apple 
and later when I feel it's not behaving as per my needs then there's always Plan B to get the Lightroom
Thanks a lot for the heads up buddy,might bother you guys with more queries in future.
cheers
Karan