Hard to say what we can expect from R19. Also bought upgrade week ago (as MSA user), but don´t know what can expect for 600euro. In case of main feature for R19 would be Prorender (btw. some interesting info on cgtalk "directly from kitchen" :), it will not be big deal (for me)
http://forums.cgsociety.org/showthread.php?f=47&t=1449143
(especially last pages, where is told about "not near future of full implementation" of Prorender into c4d if I understood correctly).
In my work I was found installed R10 demoversion on old computer (installed years ago). When start to play with, I had to say "this is the same as I use today in R18" (same interface, almost all deformers as today, cloth, mograph, BodyPaint the same (or only minor changes)... Is not that strange?
How many years are between R10 and R18... 10 or more...
edit, 10 exactly, just found on wiki