I am running Archlinux with 3.5 and 3.6 kernels on two ThinkPads (X31 and T41 from ca. 2003 with Intel Centrino processors). I can compare the performance to a 10.04 install and there is no difference. I think what is more important than the kernel is the rest of the system, e.g. what desktop environment you are using, what background processes/daemons are running, and what software you use. This determines you experience.
For me, Archlinux runs very well on those old laptops and I am happy that I took the effort to install Arch on them. Besides, Archlinux is one of the few remaining Linux distributions that provides i386 kernel which do not require a pae-capable CPU (both ThinkPads have non-pae CPU's) and that was one important reason for me to choose Archlinux.