I was dx in 2009 aged 44 (with what they call early onset Parkinsons) and from my perspective it took far too long to get a diagnosis.
I presented to my GP in 2007 intially with tremor and depression.. but it was blamed on stress and grief as I had recently lost my father. I was then referred by same GP to a neurosurgeon who took a history, did an MRI and told me 'no evidence of stroke, tumour or source of back pain' but noted my 'slurred speech, my restricted left arm movement and hand tremor' advised me if symptoms continued to see a Neurologist. I thought I just wasn't coping and PD wasn't on my radar. I finally got a direct referral (via family connections) to a Neurologist who took about 15 minutes to assess confirm his diagnosis and deliver the news.
So it was finally a specialist.. but the surgeon (who I suspect knew) missed it. The GP didn't have a clue. Which is why i replaced her. I'm not bitter but you do need to be assessed by people who know enough, about the many manifestations of this disease, to be correctly diagnosed.