Federico, you want to improve Gnome performance? It takes me about 20 seconds (yes, twenty!) from the time I type my password in GDM until my session finishes loading up. This is on a 1 GHz iBook G4.
I’ve got a few applets: clock, system monitor, battery, processor, weather, but the big slowdown is my terminals. My session opens two gnome-terminals, each with 4 tabs, and each tab is a login shell that runs keychain.
This actually got 5-10 seconds slower when upgrading to Gnome 2.14 from 2.12 — it used to only take ~10 seconds to get everything started up.