Sprint has reportedly stopped charging $0.20 per min for call forwarding (Conditional only).
Google Voice & Sprint… 11/08/09 Inside Sprint Now
I've read tons of forums, discussions, web sites, and there's a lot of conflicting information and some Sprint reps are getting confused on this, it's new.
However, here's my general understanding:
Conditional Call Forwarding:
*73 - No answer call forwading
*74 - Busy call forwarding
*28 - Busy / No answer call forwarding ***
Unconditional Call Forwaring:
*72 - Forwards immediately - Still charges $0.20 per minute
I'm using *28 as the best option. I've tested it out. When I turn my mobile phone off, it forwards immediately. I am, however, checking my charges to ensure that per minute charges don't occur, even when forwarded to another phone to talk, but it appears that Conditional call forwarding is now free (I won't bother posting the multiple links, forums, discussions, releases, etc, but you may Google it).
Please be aware that there's a lot of arguments going on regarding the accuracy of this and Sprint still does not have this updated on their web site.
I'm pretty confident that *28 is free at this point though.