I was a heavy treo user, using the treo for a phone, for work( as physician): I used epocrates as drug data-base and I kept track of hospital patients and surgery which I would code on the treo and e-mail( though pop3) account to my office manager for billing, and lastly I used audible to listen to books on tape.
I am happy to say that in a mere few days( and a 1gig transflash card) my QTEK has been able to surpass the treo:
I am running Tweaks2k2 on the phone: I have over 5,000k free
On the card I am running clearvue suite, Epocrates, Audible, PhatNotes, and TCPMP
PhatNotes allows me to keep track of patients and e-mail them to the office(as well a syncing with outlook)
In fact the QTEK 8500 surpasses the treo on its ability to read PDF on the fly( a constant treo problem), and I can listen to books on tape or music with audible,TCPMP, and wmp through my Motorola HT-820 bluetooth headset ( A feat which requires third party software on the treo which usually caused my treo to sputter, freeze and require a reset)
I was sceptical moving to a smartphone, but I loved to razorish form factor and I think Palm has dropped to ball by coming out with consecutive phones( 600,650,700) with little to differentiate them.
IMHO the QTEK blows the treo away in form and function