I will try to help since I had the Treo 700w twice and gave up and moved onto the Treo 700p. I didn't use the 3 way conference feature so I can't speak to that, but you can sync to a MAC using MarkSpace's MissingSync for WindowsMobile
www.markspace.com also PocketMAC at
www.pocketmac.net is working on theirs but its not out yet.
I gave up on the Treo 700w long before either of the MAC sync apps were fully ready and I do use both a MAC and WinXP box.
The 700w is not as one hand use friendly as the 700p, the lack of RAM (see the 700wx on Sprint for more RAM

) and you may also find the lower res screen, screen size, and the fact you will need a task mgr to close out the apps and get used to soft resets to get the RAM back.
All that said I liked it but got tired of the lack of RAM and I will NOT move to sprint for a 700wx and I will pass on it if and when Verizon gets it until I see the next Palm OS Treo and if its going to be worth the jump back.