SeaMonkey/Features/2.1

What big things do SeaMonkey 2.1 builds offer (over SeaMonkey 2.0)?

Nightly

Please provide explanations for all items here.

OOPP: Code is all there, but needs libxul, which in turn needs external linkage of mailnews.
- bug 545716 Use out-of-process-plugins (OOPP) framework in SeaMonkey.
- bug 394502 [Meta] allow SeaMonkey to build with libxul.
Places Bookmarks: Waiting for reviews. (bug 498596)
Firefox Tabbrowser API: under review. (bug 467867)

FF 3.6 and DevPreview relnotes provide some info.

WOFF format for website fonts.
Resizeable text areas in web forms (bug 442228).
Fullscreen video.
JIT tracing for x86_64.
async places history expiration.
Expiration and frecency-ordered form field autocomplete.
Improved js-ctypes support.
Better performance on startup and shutdown.
SVG attributes which are mapped to CSS properties can now be animated using SMIL (bug 534028). Support for SMIL Animation in SVG.
Core Animation rendering model for plugins on Mac OS X has been implemented. Plugins which also support this rendering model can now draw faster and more efficiently.
Support for new CSS attributes such as gradients, background sizing, and pointer events.
Support for new DOM and HTML5 specifications including the Drag & Drop API and the File API, which allow for more interactive web pages.
Protection from out-of-date plugins
CSS :visited selectors have been changed to block ways that websites can quickly check a user's browsing history.
The SSL security system has been changed to fix a renegotiation flaw.
Support for CSS Transitions.
Support for WebGL, for Direct2D acceleration on Windows (all disabled by default).
A new HTML5 parser.
New Troubleshooting Information page (about:support).
Notification bars for MailNews return receipts (MDN)
Support for libnotify-based Desktop Notifications on Linux (e.g. mail alerts, finished downloads)
Support for using system proxy settings on Windows (bug 485764).