The retries will affect battery life, of course, just as running any type of code at all on the device will affect battery life. In terms of how often the retries are issued, you can imagine basing this on a heuristic derived from things such as the current signal strength, the reason for the loss of connectivity, and perhaps even the duration of connectivity loss.
I am not familiar with the retry scheme that will be used by Windows Mobile devices in the case of a loss of connectivity.
There are several questions above regarding device availability -- as Max and KC said, there is forthcoming information on this. I myself do not know what device makers' plans are, so I'm anxious to read this upcoming blog, too.
Sami