I've got a 2006 discovery 3 tdv6 SE.
Bought for the same reason, Vauxhall is terrible, x5 and volvo thing rubbish.
It's been reliable and after having it re-mapped I can see 40 mpg in some cases.
Common faults, suspension pump for ride height, auto handbrake adjuster, brakes as it weighs a lot, steering column can rattle, nothing over expensive for the type of vehicle.
Ignore body off comments for fuel pump etc as it can be done without, make sure it has good history with regular services and you want to see bills not stamps.
I'd stay clear of base models with cloth etc unless your a farmer, interiors are poo.
I went for SE as it has a lot of toys but not too many like HSE that all go wrong, also I have no sunroofs as they leak.
Overall it's great, had it a year and will be with me for a good few years yet.
I made a few changes that I think make it stand out, it has 20 inch Range Rover sport wheels, disco 4 rear lights, clear side repeaters, side steps so the kids don't struggle and scratch it getting in and out, tinted rear windows and the re-map.