There's a very good interview with him on f1.com - not your usual interview, it's one of those 'personal life' quick-fire interviews. I read every one of these, and Pedro's is definitely one of the nicest to read. It shows just what a genuine man he is.
http://www.formula1.com/news/interviews ... 14148.html
Anyway, my opinion of Pedro? Solid, but unspectacular. I never saw him race before 2002, but from what I've seen he is actually quite a bit like Nick Heidfeld, as you say. Mr. Reliable. Never seems to get involved in silly incidents, but never seems set the world on fire (which I know is the popular opinion on Heidfeld, but I thought the first half of his career was decent enough. IMO he was better than Webber at Williams)
He scored a podium at a wet race in Hungary, where even people like Alonso spun off. Maybe he didn't get it through sheer pace, but he kept it on the track when no one else could.
As you mentioned, Pandamasque, when he stood in for Montoya at Bahrain he was a bit rusty. It was a shame, because he was actually quite impressive that weekend. The details are a bit fuzzy to me, but I remember him catching my eye, and promptly trying over-ambitious overtakes that saw him out-break himself
But, having just read about him on Wikipedia, I was surprised to find out that he actually raced for McLaren in the last 8 races of the 2006 season. I was following F1 very avidly then. I think that just goes to show - he was a bit anonymous on track, really.