Walter Mossberg, Wall Street Journal Personal Technology reviewed the THERA and basically said it is a dud.
His main points include:
1) Clumsy as phone
2) Only fair as wireless data device
3) Pocket PC based
4) Expensive $800 with 2 year Verizon contract
5) Big and Boxy; Heavy
6) No keyboard or keypad
7) Can't use as one-handed phone (?while driving)

difficult to compose email
9) No 'flip phone'
10) Poor battery life: 90 min talk/data or 8 hr as PDA!!!!
11) Phone poorly integrated with PDA (eg: can dial number from Contact list; separate address book for phone use - I can't believe this - what is Microsoft doing with all their R&D money!!!)
He also panned Verizon, due to fact that one has to connect to Verizon each time (billing on per minute basis) and 1X not being anything to write home about.
Remember, it takes Microsoft three tries to get it right. The Thera compares well with Windows 3.1
Bob