I am firmware updating my 5400 currently. It is a nice radio, form factor of the x90 portables, yet it allows the switch to serve as the function key, much to my pleasure.
Programming is atrocious to say the least. Not only is it like programming a motorola, you can not see all of the channels or zones to ensure everything is honky dory. It also sports a 16 channel knob, not a free spinning knob like most kenwood portables.
Ebay has plenty, the gal selling them for $200 in LA drops the price occasionally.