I'd LOVE to tell you. And as soon as Steinberg comes back online, I'll download the update and let you know, LOL...Their site has been down for 24 hours now, due, no doubt, to a couple of million of us attempting to get at the patch!!
Why don't you head to www.cubase.net ?
Check out the various forums, do a search maybe? You'll find lots of info re 5.04.
BTW, the latest version is 5.05PB2 (public beta) . I have it installed and it works fine in my Asus CuBX PIII700 with RME Hammerfall card.
Visit the public beta forum(s). In the announcements section you'll find a list of things fixed, known issues etc. Read the threads, they are very informative.
For what its worth, I noticed that r4 fits better with the tascam US-428. The select button brings up the mixer channel and effects pages for the track. Convenient.
Some appearance changes here and there. I few other things I noticed were smoothed out when I first got it, but I didn't pay too much attention after the first few days. Didn't seem too drastically different than 5.0 to me.
I got the path off www.cubase.net just fine about a week and a half ago.