One of the things I always hated about Sprint was the fact that they charged $0.20 for conditional call forwarding per minute. You also had to call Sprint to get it turned on! Conditional call forwarding is necessary for voicemail services like YouMail, Google Voicemail, & PhoneTag to work.
As far as I know most of the other major carriers offer this feature in different formats. For example, on my AT&T account it just gets counted against my minutes. I remember on T-Mobile they gave you a bucket of 500 conditional call forwarding minutes after which they charged you. I am not sure about Verizon but I think they also just deduct it from your monthly minutes.
The crazy part is that this brings Sprint from the worst policy to the best policy. According to their statement I found on MobileCrunch:
Conditional call forwarding for busy calls or calls not answered using the customer’s wireless phone will be free, beginning mid-November. (Standard charges will continue to apply for immediate call forwarding.)3 This change will give Sprint customers the opportunity to access third-party voice services, including the new voicemail feature in Google Voice.
They will not be charging at all for call forwarding minutes! That is better than any carrier I have ever heard of. Sadly these changes only take effect in mid-November so hang in there!