I don't think you'll see any difference in office programs, flash or internet browsing between those chips.
My desktop (AMD PII 965 x4 @ 4GHz) and laptop (P T4300 dual core 2.1GHz) both do the basics to the same standard. I think the HDD in the system would make more of a difference than CPU...
Anyone know when the AMD sleekbooks are coming out in the UK? I read some point in July, but can't find an exact date. Ebuyer, at least, said in an enote that they aren't planning to stock them at all...