I have been using normal GPRS plans on 3G network without any issues over the past few months. I have tested them on Idea and Tata Docomo networks so far. The downside of this is a speed limit of 128 kbps (approx 16Kb/sec) on the 3G network. But, this makes sense as you pay for a 2G data plan and use on a 3G network. Here is a list of pros and cons of doing this -
Pros – Using 2G Data Plan on 3G
1. You get a more stable internet connection.
2. The speed is lot better than what you get on 2G.}
3. You can do Voice Chat (Superb Quality) and Video Chat (Poor Quality).
Cons – Using 2G Data Plan on 3G
1. Slow speed @128 Kbps, capped as you are using 2G plan on 3G.
I feel this is great given the fact that 2G internet is unreliable and very slow for normal browsing. There are a number of plans that can be used with Tata Docomo. If you are a casual user just interested in voice chat and general facebook browsing, emails and occasional downloading, Tata Docomo provides the cheapest plans -
For Idea also, you can again use the normal GPRS plans on 3G and get a speed which is capped @128 kbps. For Vodafone, this is not possible because for accessing the 3G network, you need to subscribe to a 3G data plan.
I see the usage of 2G plans in 3G networks as a well thought plan and not some kind of a bug or a hack. This prevents the cellular companies from receiving complaints from the consumers when they accidently tend to use the 3G network and have their balance deducted. In a normal scenario, if you are using your 3G mobile in a dual mode, when ever a 2G network is weak, the phone will automatically switch on to a 3G network and vice-versa. In such a scenario, it makes sense to provide the mobile user, data connectivity even in the 3G network at a reduced speed, thus minimizing pressure on their call centers due to unnecessary complaints and also preventing accidental balance deduction from the customers account. This way both the users and service provider are happy.