Just had this very discussion with a relative. I previously had a SR 2.2 MBP with 2GB ram, 120gb HDD as my laptop and to be 110% honest I cant really say I notice any speed difference and this is both in relation to disk access (4200RPM - 5400RPM) or in general usage of my applications (CPU wise).
I'm mostly surfing the net via safari, checking email in Entourage.
Quick blogging on iweb, touching up or making edits to other websites I've done in Freeway Pro 4. Minor corrections in photoshop cs3 along with just previewing documents to clients in illustrator or such
I have another client who is currently working in pages (instead of word) to write a book so I get draft copies and I read them on my MBA and again of course absolute no difference peformance wise that with my previous MBP.
Of course i'm not manipulating 3D, playing graphics intensive games, or rendering or encoding stuff - but I never did that on my MBP either.
The most CPU heavy thing I do is Corel painter X and again I can't say I have noticed any difference in performance.
So yes for me - like yourself cybergypsy the MBA is producing the exact same experience as my prior 'more advanced' laptop.