The 2820 is an excellent radio.
I have no gripes about this radio at all... (Well maybe the price..
The receiver is very good even is strong RF areas. Audio power is good also.
Transmit audio is very nice on both analog and digital.
Icom did a good job on the usability of this radio. Even when mobile, the menu system is easy to use.
The display is packed with information.
This radio is setup very nicely for D-Star use.
The ID-800 is a great radio also. Transmit and receive are very good also.
Since it has the smaller display, its not as easy to work with.
This radio was more of a first generation D-Star radio so it doesn't have all the niceties that the 2820 has. But it is a very capable radio.
As you would expect, software is is pretty much a necessity for both radios.