I haven't seen any performance improvement for OpenLaszlo apps, but I haven't done much testing. JSON parsing will be much faster, since there is native support for it now. With the upgrade to the 4.5.1 SDK OpenLaszlo could support stage video (giving you much better HD video playback performance), but you'd have to write a new videoplayer component for that.
On mobile devices, the performance should be much faster, which would be very valuable for native apps generated using the AIR sdk as well (both iOS and Android). It would be nice if the Webtop team could report back their experiences with the swf11 runtime. Sebastian and the OpenMeetings team will welcome swf11 for the new AV capabilities (which should be very attractive for Laszlo/Webtop/CP, since it includes features like background noise suppression and G.711 audio compression for telephony). The garbage collection process could be optimized for an application, which could give you a much better performance in certain situations, and the new LZMA compression can reduce the SWF file size of applications by up to 30%. - Raju
