As Kennyt above, I have also done direct shootouts in home and found the S350 best video and functions, speed of loading, price, blu ray capability and SDVD capability the absolute best, and S550 has all of the above but if your looking for more audio performance s550 is a edge better and both far better than others available..
A thread on this subject from this site I attached below, with very in depth reasons and differences of all these players including the current oppo without blu ray which will be the same player doing blu ray soon, but if you like about 90% of the others have no use for SACD then you do not have to pay double the price and wait for this oppo, which honestly if you are heavily invested in SACD it would be obvious you have a good capable player already and no need to try and go with a new universal machine.
Besides today technology has moved on, sony failed with SACD and won with blu ray, and already now Hi res downloads and Blu ray audio is beginning and the future of audio formats so if you can even find a SACD disc today good luck, of course online you can order them! Funny because sony dropped SACD from their machine just after everybody else started adding it, and now they invented blu ray which is quickly taking over and they do have the best machine in performance, speed, and build quality available for the right price. Anyway my only point is don't wait on oppo at this point for the wrong reasons.. I have only had oppo in my system for nearly 5 years with nobody coming close, this is now a different story.
The s550 is also which is unknown the only player that has the full out of the box 2.0 profile, along with USB memory included from sony, and is the only stand alone Blu ray machine in picture that beats the PS3 which is of course based of the same platform etc
. The s350 needs to have the Memory added which you buy, and upgraded online, and does not do all the True HD dolby whatever formats.. Only the s550 does and Oppo will basically copy this and possibly add SACD and DVD-A
So in the end the S550 even if you gotta pay 50 to 100 more to order it is worth the extra in my opinion, oh and it is a much beefier transport physically. The S350 is currently the smallest body blu ray player (most compact) from any existing manufacture, which is interesting because the sonys also weighed in much heavier picking them up!
Finally the S550 is the Fastest and Quietest being all these blu ray players have internal Fans... You put your ear down by the others and you will hear them.. The sony is virtually dead silent..
http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1230738445&openmine&zzUndertow&4&5#Undertow
