It's a very complex question since the answer depends on the precise circumstances. Do I think its ok to break the speed limit on an empty 4 lane motorway? Do I think it's ok to drive at the 30mph speed limit past a busy school at picking out time? no...
I would argue that the large-scale downgrading of limits (NSL to 50, 30s to 20s) where not always appropriate (though not always inappropriate) has something to do with that. In some places, e.g. Derbyshire, the majority of what were NSL roads are now 50s.
If you want people to respect speed limits then they have to be justified. It used to be the case that they were set at the 80th percentile of the speed of traffic and that this worked well in terms of having limits that were both credible and likely to be obeyed. The danger in setting speed limits too low is that people will be habituated to ignoring them, particularly those that are unjustified, and then will one day find themselves ignoring a well-justified limit to the detriment of other road users.
Driving well is all about judgement and situational awareness so there is really no reason why a rigid attitude to speed limit adherence is necessary in a 'good' driver. All that's needed is a mature one.