Personally I'd either get an RTG card and run OS 4.0 on your PPC or forget you've even got a PPC (unless you're into games..Wipeout 2097 etc).
I run OS 4.0 on a Cyberstorm 233MHz at 1920x1080 via a CVPPC and it's plenty fast for me. Icons are drawn fast...the only major slowdown is when dragging a busy window (i.e. OWB) but, other than that, I'm more than happy with the performance. That's with 128MB RAM which I consider a must have as I frequently get down to < 60MB free...the OS/software either leak like a bugger or it's got some sort of lazy garbage collection.
Did have a couple of AmigaOnes but got bored to death with OS 4.1 and, for me at least, it never felt like an Amiga...just another computer to get frustrated at over the weekend that had an OS that reminded me of the 68k Amigas. At least with a PPC classic you can use OS 4.x and still be on a real Amiga which, for me at least, is important.
To be honest, unless I'm booting 4.0 I forget I've even got a PPC unless I run SysSpeed or WhichAmiga which jolts my memory for me. They're fun to have and fun to own but, for all intents and purposes, I'm certain they only sell for the money they do because they're the bees knees for classic Amigas. Whether you actually use that functionality is entirely a different story and, if people took a real hard look at them and what they offer, the price would be nowhere near as high imo.
But that's just my opinion. I was hoping this thread would turn up some little gems and show my ignorance on the matter but, thus far, nothing seems to have appeared to change my mind.
As an aside it would be an interesting poll to see how many people with PPC accelerators use the PPC on a regular basis. I suspect more than a few would have used it once to maybe verify it was working or 'have a play' but forgot about it since and stuck with 68k.