I have used my Treo 90 for five years now with not a single problem. After they were discontinued, I bought three extras thru eBay and am changing them like bedsheets, once a week. (They backup each other this way.)
Only one has required a battery replacement which took five minutes and cost about $11.00.
If you are buying a used one, be sure to ask the seller if there are any yellow blotches on the screen. They will get bigger eventually. Pass on any with blotches.
This little PDA, along with the Palm software, has been bulletproof. I love it.
I don't believe in the phone versions because if one part breaks you lose both systems for repair.
The Handspring Treo 90 is a handy little pda with a built-in keyboard. Although the keyboard is small I prefer it over using the graffiti method used with many of the Palm pda's. This unit has been extremely valuable for both my work and home environment. The 16MB of storage is very adequate for my uses. I work in the medical field and am able to store and access drug information quickly and accurately. I also use the Treo 90 to run calculations, organise my calendar and store addresses for personal and business contacts. This product has made me more productive at work and keeps me organized at home. I love the handspring treo 90 and would be lost without it.