I'd a Psion 5 Mx and loved it. It had one of the best small keyboards. It's folding mechanics was superbly engineered.
Later I switched to a Nokia 9210 Communicator (Nokia Series 80), basically a Psion 5 with networking and phone integration and a nice screen.
My living-the-future-moment was in the early 2000s sitting in car on the phone, then opening the phone, automatically switching to speakerphone and loading a spreadsheet to check some data. Later I emailed the sheet to a colleague and send the sheet as a fax from the phone to a customer. All from a single device.