Idea platinum 3G is not good in Delhi. I get only 1.5-2 mbps download with idea 3G 900. In delhi we can also latch onto Vodafone 3G with an idea sim. With vodafone 3G network I use to get 7-12 mbps.
I think 900 mhz spectrum get too overcrowded due to larger coverage per BTS thats why we get lesser speeds.