A list from http://arstechnica.com/journals/apple.ars/2007/1/10/6559 By Mary E. Tyler.

Here is the brief.

• Cost
• Cingular
• No 3G
• No WiFi sync to iTunes
• o over-the-air downloads from iTunes stor
• No removable memory
• Battery life issues
• No MS Exchange or Office support
• Not extensible by third parties