I've got an N450 Atom netbook that outperforms my old Pentium M 1.5ghz laptop by leaps and bounds. Granted the bus speed is much faster too now, but I can run Firefox with a bunch of tabs, encode a DVD to xvid and preview another DVD iso without everything stuttering.
So to the point...you are right on about the Atom. More power and a lot less watts being used. If you have the money, upgrade and follow the three R's for your old junk (junk is ((a))relative).