I just did the upgrade. It went very smooth, very easy, no problems at all. Now I can record video on my HD camcorder, edit it on my Sony Vaio, burn it to a BD disk and play it back in the Samsung. Until today I could not do that, so the upgrade was worth its weight in gold!
Picture quality looks the same to me, but I have not had any complaints about pq with the Samsung and I also own the Toshiba (I have been arguing that there is no difference in quality between the two, just in the software being viewed).
No difference in audio quality that I can detect either, and here too I have been very happy with the Samsung audio.
Startup is ever so slightly faster, but nothing to hardly even mention.
So, the main difference as far as I can see is the ability to view blu ray disks recorded from my Sony Vaio.