We have the Sony BDP-S300 and we've recently loaded 3.95 firmware that Sony sent to us free in just 2 days. Before our purchase, we looked at the Panasonic, Phillips and Sharp players, but then decided on the 300.
I have nothing bad to say about it, in fact, I'm very happy with the player. It plays Blu-ray disks and standard DVD's very well, while I expected the Blu-ray format to look good, which it does, I was surprised by how well it upconverts standard discs as well. All video, regardless of the format looks really good.
Audio-wise, I have the BP audio set at PCM over HDMI to our Harmon/Kardon AVR receiver, which is set on Dolby Digital (5.1) and it sounds absolutely awesome. Crystal clear and the dynamic range is quite impressive.
I've heard about the long disc loading times, but the v. 3.95 cuts down on that and to me, I don't really notice it anyway. Turn on the power, it then powers on for maybe 30 seconds, but it's ready by the time you have the disc ready and then another 30 seconds or so to load the data and you can play it. I don't see that as any big deal. I couldn't imagine buying another player because it may load 10 seconds faster as I couldn't care less about that.
As far as performance goes, I'm happy that we chose the Sony player and I can easily recommend it.