This page explains the changes to infinite sessions pretty well. It also mentions when everyone will get the new Facebook UI.

Quoted: Q: I thought you were deprecating infinite sessions?
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A: We are deprecating infinite session keys after the new profile launches to all users August 27, 2008. However, if a user previously granted an "infinite session" (what we're now calling "offline access"), then that user will be considered to have granted your application offline access and your sessions will continue to act as they did on the old profile.

Quoted: Facebook offers some API functionality which requires specific opt in from the user. These methods are specific to certain use cases and require a greater level of trust from the user. They therefore employ a secondary opt-in flow, and the user may only opt in to one such permission on a single page view.
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This permission grants an application access to user data when the user is offline or doesn't have an active session. This permission can be obtained only through the fb:prompt-permission tag or the promptpermission attribute.

Listing of the new facebook APIs.

Including Feed.publishUserAction.

New .NET Facebook API on CodePlex.

Quoted: Recent changes to the Facebook API are being evaluated and a Toolkit update will be released at the end of this week as a point release (version 1.7). We are planning to address the changes to the platform that specifically cover the new user profile design and session changes to many of the existing methods.

Ha. When returing FBML pages from your facebook app, you can't redirect to a new page using a standard 302 response. Why? I don't know. Facebook will however parse the FBML for a fb:redirect tag and request that.

Quoted: Redirects a user's browser to a new URL within the Facebook canvas.
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<fb:redirect url="http://apps.facebook.com/myapp/?not_in_group" />

Redotting Mike. Cool.

Quoted: Correlation is not causation, of course, so we can't say whether the decline in developer activity means less application activity, if developers are leaving because applications are no longer as successful as they used to be, or whether there is an unknown factor causing both of these phenomena.
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What we can say is that the vitality of both the Facebook developer community and the Facebook platform is not what it was even four months ago, and that these two phenomena are closely related.

An overview of Facebook's upcoming profile changes for developers.

Quoted: We’re getting ready to launch some significant changes and improvements to Facebook, including a new profile for users and a new navigation bar for the Facebook site. These changes are intended to help users communicate and share information more easily with each other - on their profiles, through applications, and through News Feed.