Vodafone was the quickest to respond to my request, and I got my connection within 2 hours of asking for it on their call centre number, with activation taking another two hours. Their customer service and other staff were incredibly efficient, courteous and knowledgeable.
I think Vodafone’s 3G was the best of the lot, with speeds of at least 1.5 Mbps and maxing at 6.5 Mbps late at night. Coverage was decent in cities and highways, but nonexistent in rural areas.
However, there was one really big drawback to Vodafone’s 3G, which is that they don’t have any method of checking usage, which is just silly, because they have no unlimited plans, and they charge you after a certain free usage that you pay for with a monthly charge. This pretty much means you would have no way of knowing when you cross your limit, and the bills start increasing at an astronomical rate.
The only thing Vodafone was able to offer me to counter this was to call the customer support line and ask for your unbilled usage, not including discounts and free usage. My unbilled amount climbed to Rs. 22,000 before I put a stop to it and disconnected my service! Thankfully, after deducting free usage from my unbilled amount, my bill was only around Rs. 1,900.
Conclusion: If you can keep track of your usage reliably, and want to use it only in the city, Vodafone 3G is your best option. Don’t panic on seeing huge unbilled amounts, though, it’ll probably be greatly reduced once free usage is deducted.