I don't know about thegman, but there are certainly a number of Select features that I'd like to see on the Iyonix, from an end user point of view.
Just a few that spring to mind are the following:
Writable icon cut and paste - allows text in icons to be selected for cut and paste. This is such a simple thing, but makes such a big difference and must be part of every other WIMP system under the sun!
Sprites with alpha channels - allows you to create and use icons with variable transparencies, providing proper transparent drags, and proper anti aliased icons independent of the background, for example.
Better network sharing - you can share individual folders rather than whole drives.
Better configuration - for example, network configuration changes occurs immediately, instead of needing a restart.
Better apps - Paint, Draw etc. are improved.
That's just a few things off the top of my head and there are many more. Most of these are UI changes, so it really ought to be possible for them to be layered on top of RO 5.
Having said all that, I do personally really enjoy RO 5 as well, and it also has benefits over Select: things like pop up printers, nice USB funcionality (USB drives just appear on the icon bar), large application task memory, Internet updates, very fast boot time. These are also important from a user perspective and I'm not sure I'd be willing to lose them to gain the Select benefits.
Sorry for the long post. It's just that in my opinion RO 4 and 5 each have some great unique features and I don't know of any proper comparison that highlights the stengths of both.