Sunbird: penalty for not starting out with Lighning? address book architecture?

Hi, I've just started using portable Thunderbird and Sunbird. I like the idea of address book integration but the public calendaring stuff leaves me cold in an age of snooping.

My current plan is to continue until Lightning and Sunbird are past the 1.0 hump and then move from Sunbird to Lightning. Here is my question:

Will I experience any more pain moving from Sunbird to Lightning in, say, a year as opposed to starting out with Lightning right now? My guess is that standalone Sunbird is a little more mature just based on version numbers--please correct me if I'm wrong. Also, I want a rock-solid Thunderbird app since I depend on it for email, which inclines me to caution. I expect a future cutover from Sunbird to Lightning to be easy given their close relationship (or perhaps even identity to a large extent).

Also, is there a way to get Sunbird and Thunderbird to share the Thunderbird address book without one being an extension of the other? I realize that this is harder to accomplish between two freestanding processes than in the case of Lightning, but I'm still curious to hear whether the architecting of the Thunderbird/Mozilla address book contemplated sharing by multiple concurrent processes. Any comments?