My Centrino is great. I can run flat out on batteries for about 2 hours ('always on' mode
for audio work), or 5 hours on battery-saving modes, useful for working in the library
etc. Also consider Pentium-M laptops with 802.11g wireless networking as these are the
same processor just with a faster wireless network card. They can't be called Centrino as
Centrino refers to wireless-b cards.
Faster is not an absolute. I think Martin Walker did some tests and his conclusion
was something like (for Audio software) a 1.5Ghz Pentium-M was equivalent to a 2.6Ghz
Pentium-4 .... or something like that anyway. Have a google for comparisons, and browse
the old forum too.