I am using Sify as backup, because I need 100% UP time for internet. I have taken Sify on RF (Radio Frequency) with 256 KBPS speed because this is maximum speed they give in day time.
I have taken it because I already have BSNL and I do not have any other option at Kurukshetra. I am using BSNL as Primary and Sify as secondary i.e. if BSNL goes down.
Sify technology is very outdated, they are giving connection on Free Radio Frequency, due to which they are unable to offer high speed. They are getting connection upto one office in a locality and then connecting others on a LAN, so no one has exclusive internet IP, which will make some applications like Games to not to work if they need dedicted socket connection OR you cannot host servers like Mail, web etc.
Also, it is not safe. It is strongly not recommended unless you do not have any other option like me.