[johnhiler]

That’s a really high number of posts and pageviews!

My bbPress forum is # 12 on that top100 list. It’s not nearly as large as your phpBB site but I’ll share the scaling problems I’ve come across, in case it’s useful.

Probably the biggest problem I face is that the Google Sitemaps plugin doesn’t scale very well. I believe the most popular Sitemaps plugin regenerates the sitemap upon every publish; this hangs my site every time someone comments on a post. I’m actually exploring the possibilities around upgrading or programming the existing sitemap plugins, to provide a more scalable solution here. But without a good solution here, my content isn’t as Google friendly as it could be.

Also, the Akismet spam solution is decent… but the bbPress moderation management tools aren’t as robust as they are on WordPress. So moderating the spam queue takes a decent amount of time a day, especially as the site has grown larger. If the problem continues to grow, I’ll look into plugin solutions to help out here.

Finally, the account management tools on bbPress aren’t very robust. For example, I get emails every day from users saying they forgot their username, or would like to reset their password. bbPress doesn’t currently have easy ways for users to retrieve a forgotten username or to easily reset their password (they can reset the password, but first they have to put in a username/password and fail a signin attempt). I’m actually working on plugins and theme changes to address this one now, but it currently creates a decent amount of work answering emails from confused users.

My final concern actually is around bbPress 1.0. I am very happy on bbPress 0.9, but version 1.0 is around the corner and seems to be a lot less lightweight than the current version. I’m also concerned about the lack of backwards compatibility with some 0.9 plugins. This wouldn’t be a huge issue, but bbPress 1.0 is currently necessary to ensure cookie/signin compatibility with the latest version of WordPress.

If you are considering bbPress as a standalone forum for a huge site, I’d definitely recommend it – as long as there are plugins for all the features you currently support on your forum.

If you’re considering bbPress in conjunction with WordPress, I’d hold off until bbPress 1.0 comes out of beta and/or a plugin supporting bbPress 0.9/WordPress 2.7 cookie integration comes out.

Just my two cents… hope that helps!