If you have styles associated with a registration, and you're in another style, you merely DON'T TOUCH the registration buttons if the FREEZE light isn't on.
Look: You can set up one registration button only, and you are ready to gig. Just set up one registration button with your global preferences. Turn on the keyboard and load that registration. Now the mic reverb, harmony settings, and everything else is where you want it.
Create OTSs for your favorite floppy styles for which OTSs don't exist. If you use that style for only one song, save the style at the desired tempo.
For my Christmas gigs, I have all of my favorite Xmas styles on one floppy. Each style is named after the song and set at the desired tempo. Each style has four OTSs perfectly suited for that song. All I need to do is pull up the style, transpose if necessary, press an OTS, and start playing. It's easy as pie. I don't even use registrations, except to configure my global preferences. At some point I'll start using the registrations for voices, I don't need them for styles.
For preset styles, you can either save them to a floppy or as USER styles at your desired tempo, or pull them up, quickly set the tempo and the transpose if necessary and away you go. The advantage of saving the style to floppy or user memory is that you can create a custom OTS.
If you prepare your keyboard and your style floppy well before you gig, you really don't have to do that much while you're playing.
The only reason why the PSR740 is a walk in the park is that there isn't much you can do with it. You can't create your own OTSs or more than three USER styles, and you can't access the registrations easily so most people wouldn't use them.
The only major disadvantage I experience with the PSR2000 is when I want to get that simple intro in the middle of a song. I have to be in the main screen and press two buttons before I press INTRO on the PSR2000.
It takes a little bit of learning to get used to anything new, and I also felt a bit attached to my PSR740 when I first started, but now that I'm up and running with the PSR2000, and I see the way my clients respond to the music, I'd almost feel embarrassed to perform with the PSR740 now - especially because the mic output is so superior on the PSR2000.

Larry