There is not much different on the exterior model, a few texture improvements here and there.
The panel & VC are where most of the work has been done, with an updated flight model too.
Updated Panel & New Virtual Cockpit
More detail & more systems.
The manual has been updated with all the new features - Comet Manual
Also a new flying guide which goes though the panels new checklist - Flying The Comet
New Flight Dynamics
Much better balance between power & drag. Not so racey after retracting the flaps.
Other changes are mainly to do with new panel features.
Extra sounds The panel now makes use of Doug Dawson's widely used method of adding sound effects to XML gauges.
Extra sounds added are:-
Takeoff config warning (if flaps & tail trim not acceptable for takeoff)
V1 & Rotate co-pilot calls
All of these sounds are non-standard FS sounds & are actually included with the panel download.
If for any reason you don't like the extra sounds, they can be removed by deleting this line in the panel.cfg file:- gauge32=dsd_xml_sound3!dsd_xml_sound3, 2,2,5,5,.\Aircraft\DMFS Shared Files\DH106 Comet 4 Panel VC\DM_COMET_sound.ini
In addition, the normal FS sounds for Stall warning (stick shaker) & overspeed have been upgraded to use more authentic noises. These two sounds are standard in FS & so are included in the Sounds download.