I can use it in Gujarat and Delhi, as I plan to...no roaming charges. Not decided on MTS as yet.
You are right. I was of the impression that they charge roaming just outside home state (the state from where one has got connection)
An excerpt from their website, clears my misconception, though the first para infers some confusion, if one does not read second para.
National Roaming
Now enjoy Data services in roaming locations like Mumbai, Maharashtra, Andhra Pradesh, Bihar, Haryana, Punjab, etc with speeds upto 3.1 Mbps. This means customers can now enjoy data service outside the MTS home states of will be treated as roaming. Speeds 3.1 Mbps is subject to service availability of partner operator.
MTS home circles: Delhi, Rajasthan, Kolkata, Rest of West Bengal, Gujarat, UP(W), Karnataka, Tamilnadu & Kerala.
Services outside these circles will be treated as roaming circles.