IPv6 network boundaries vs. IPv4

[John Osmon <josmon () rigozsaurus com>]

Is anyone out there setting up routing boundaries differently for
IPv4 and IPv6?  I'm setting up a network where it seems to make
sense to route IPv4, while bridging IPv6 -- but I can be talked
out of it rather easily.

Years ago, I worked on a academic network where we had a mix
of IPX, DECnet, Appletalk, and IP(v4).  Not all of the routers
actually routed each protocol -- DECnet wasn't routable, and I recall
some routers that routed IPX, while bridging IP...

This all made sense at the time -- there were IPX networks that needed
to be split, while IP didn't need to be.  DECnet was... DECnet -- and 
Appletalk was chatty, but useful. 

I keep hearing the mantra in my head of: "I want my routers to route, and 
my switches to switch."  I agree wholeheartedly if there is only one 
protocol -- but with the mix of IPv4 and IPv6, are there any folks
doing things differently?  With a new protocol in the mix are the
lessons of the last 10 (or so) years not as clear-cut?