Well "slow" is kind of relative, what you might think is "slow" may be normal, or maybe not.
Do some searches for "memory" issues,.
I'm not sure if the Alltel comes with X-button, but if not get v1.5 or 1.51, it is a program that actually closes programs down completely instead of just minimizing them and keeping them running in the background affecting speed.
Get OXIOS Hibernate, it is a memory reclaimer and works great, also there is a speed hack if you look in the registry edit section #6
http://forum.ppcgeeks.com/showthread.php?t=5108
but it has mixxed reviews as to it helping or even slowing it down.
There is also another reg edit I used from the 6700 days (GLYPHCACHE), look in this thread
http://forum.ppcgeeks.com/showthread.php?t=10107
Of course sometimes there are just lemons in the big 6800 pool and maybe you need a different one.