The Mackie's EQ is pretty rubbish for recording bands and conventional studio stuff - People complain that it sounds harsh and unmusical compaired to the likes of the Allen & Heath GS3000...
(The Strokes first album was mixed on a Mackie 8-buss)
But... The harsh EQ suddenly becomes "modern" sounding when you're trying to EQ a breakbeat or a drum machine... So it's really the industry standard dance/electronic music desk for that reason.
The 8-busses are quite prone to breaking down though... I've had mine 5 years and I've got a few channels out now - Mainly thanks to Logic crashing and frying all the outputs.
If it needed replacing I'd consider an Allen & Heath very seriously... R&S Records used to use an A&H at their studio in Belgium... You can tell a lot of their recordings had a much warmer, softer sound than you'd get off a Mackie.
It'd be very hard to compair a software mix to a desk mix fairly... With software you can't really drive the pre-amps, and the EQ works very differently...
I'd say, if I did a very average mix in software and then tried to replicate it on the Mackie (not using any desk EQ of course) it'd sound very similar after being recorded back down to digital and dithered, etc... Although some people notice the track separation and added depth a lot more than others...
But, an analog desk does allow you to go nuts a bit - The reverbs mix in MUCH better too... Feels like you've got an extra-dimension of control on an analog desk - You can have the levels high and get a really full sounding mix, or you can leave them low and get something really subdued sounding... There's softclipping and all sorts going on inside.