I've explored my Tyros3 for 2 weeks so far and am willing to share my experiences with you. I've seen that nobody seems to be waiting for positive feedback, so I'm just concentrating on points that need approval imo :

Housing:
It's absolutely HUGE !! I think it's depth is just to much (like T1+2), it's all empty space you carry around and I find that very inconvenient. I use it more for studio use, though.

Styles :
Sound nice OTB and there's a lot of them.
If I even use standard styles, I find I'm shutting up nearly all the accompaniment parts, because it's a complete chaos : too many parts, too many instruments...your sound is becoming a "blur" that way.

OTS settings :
it really pays of to walk through them, as there are some really good settings according combination voices/harmony and EQ settings. Take for instance the Jazz Tumpet (SA2) who's effects are balanced in a way that it truly sounds like a muted trumpet.

"Music Internet Direct/ Music Finder +" :
This is a website you connect to with your Tyros. It's the biggest piece of crap I've seen to date! Even the characters in the input page (numbers and letters) aren't cached, so they have to reload everytime you switch from capital to normal letters and so on.
Every single song/setting has to be seperately downloaded (because there are too few "collections") and if you've looked at the "details" page, you're only way back is starting again from the root menu (music finder +).
It's a very powerfull idea, but the site is so userunfriendely I could go on for hours complaining about it.

Yammie's way or the highway :
I hate it that Yammie's preset styles and sounds can't be overwritten with your own custumized sounds/styles : now the tiniest adjustments lead to having everything I use being grouped under the "custom" buttons.
and you can sure customize a lot !

Compressor :
If everyone who complained about the concert grand patch being "thin in the middle" knew what a compressor whas and would have bought real speakers, we wouldn't have seen that remark so much. I find the standard compression setting the problem in cutting the C3-C5 range off too much. I've had the concert grand against a CP-300, and it's definitely the same sampled sound (I dunno if it's the same samples though!). But with al my tweaking skills, I can't match the warmth and depth of the CP-300. It just is lacking soul in some way.

EQ :
Yamaha could have made the T3 sound FAR better if every part would have it's own 5-range EQ : the overall EQ is a 5 range, but on a part (left,right1,right2,etc) you only get a 2-range EQ, aka bass/treble. For someone who wants to get the most out of the tyros, this absolutely stands in the way ! This is IMO related to the complaints about the concert grand sound not matching the demo's : I don't think you want to hear a style or a guitar with the EQ settings used in the demo for the piano solo !
Yammie dares to say in it's manual that every part has it's own high-quality EQ. High-Quality EQ means 5-range EQ per part and not bass/treble !!
I now work around this by recording each single "instrument" solo, with customized "overall-EQ" seperately on a (external) HDD recorder. That's not what I was expecting to do and this is without any doubt the issue that gave me a dissapointed feeling of this "musical workstation", also considering the pricerange it's in.

EFX
The EFX department is great : finally semi-pro effects are available. It's just a shame that OTB the EFX on styles as well as sounds are just WAY too much ! This takes away the "live" sound : too much reverb and chrous. Suprisingly often too little DSP depth though!

Overall :
I'm very pleased with my T3, but as I stated above, there are some issues that need improvement. It's an arranger and definately not a professional workstation.
For the home-user or "midi-file-performer" it is complete overkill and they will not uncover more than 40% of it's potential.
For the pro it will sadly be a work-around-station, but it's worth the effort if you hear the results !

I think the way to go for the T4 will be to consult super-users worldwide in a virtual community and for once build a flagship workstation that fits flagship-users. I'd be happy to take part in such a thing, and I'm guessing I'm not the only one, hey ?