My first general impression of Tyros 5's sound was that the highs shriek a bit to much for my liking.
This remark kind of worries me, especially because is in agreement with something that Ian posted a few days ago (about the Tyros 4 having a "sweeter" sound, compared with the Tyros 5).
From some of the demos I've heard of the T5, I've also noticed the sounds appear thinner of even 'tinny' until you apply some tweaking. Although many people might be ok with doing the tweaking, I prefer the effects already applied to the sounds on my T4 ootb, I don't really want to waste time trying to create new registrations with hundreds of adjustments. I really like how both the T3 and T4 sounded by default. I'm sure that the T5 can be made to sound incredible but this requires the effort first whereas with the T4 it sounds fantastic as it is.