I was (un)lucky enough to have a GP450 in my garage for 3 months, I was looking after it for a guy who had a pretty serious injury. For a bike that was less than 9 months old it looked pretty shabby and when I rode it it 'hunted' and wouldn't tickover and this after he had spent a small fortune on upgrades and CCM had it back twice to sort out 'issues' .
On the other hand PaulinBont rode his all over europe without any issues, to me they're like the KTM 690 enduro, great in theory but not so much in practice.