[johnhiler]

The latest WordPress is definitely the most secure, b/c Automattic has not released security patches for earlier versions. But bbPress 1.0 is not clearly more secure than 0.9 – in fact, because bbPress 1.0 uses BackPress, it’s possibly less secure. Plus 0.9 has been stable for a long time, while 1.0 is new and still has a fair number of bugs.

Integration is easiest when you share a user table. It’s possible to integrate bbPress with other software (WordPress, or even something else) without sharing a user table but it’s not easy and there are no publicly released plugins which allow it.

How many users do you have on your WordPress install?