When is it slow - while browsing, using a particular program?
Try running 'top' from a terminal, to show you what, if anything is hogging the resources.
I use BLAG & Gnome on an eeepc 1000h, which I believe has similar specs to your Acer (same cpu, at least). However, I find flash can slow firefox down, so consider installing the Flashblock plugin in FF.
You could also try using openbox as window manager, which should speed things up a notch while keeping the desktop looking familiar:
(as root, in terminal)
yum install openbox
From the login screen, click on your user name, and then select 'Gnome/Openbox' from the box labelled 'Session'.