Here is a quick summary of this plan you guys probbably missed a few bits when you say you can download enough.
Monthly charge : Rs. 500 /- comes down to Rs. 417 /- if you pay 5000rs for 1 year
Speed: 256 Kbps to 2Mbps
Limits: 2.5 GB for usage during the day 8 am to 2 am next day
Night Unlimited: YES (from 2 am to 8 am)
Extra charge if traffic exceeds imposed limits: 80 paise per MB
Minimum hire period: 3 months
Security Deposit: None