Any universal app will run faster on an Intel portable than on a PPC portable. The majority of the time, the same is true for Intel desktops and PPC desktops too.
Both pages and keynote take around 8-9 seconds to start up on both my Intel Macs, and IIRC, it took well over 12 seconds on my old iBook. I too noticed lag when typing on my iBook, but not on either of my Intel Macs.
The apps will run even faster on the C2D Macs, as both mine are now-lowly Core Duos.