SSO and I (and a couple of others from here too...) 'frequent' a couple of private forums littered with McLaren owners who will speak more openly than they might on some of the more open forums about their issues. I don't intend to share anything they might say specifically here, that's not cricket, but they tend to be quite common. Rarely big mechanical issues but tonnes and tonnes of small niggles (electrics, paint, corrosion, parts) that can and often do take a long time to resolve, weeks, months and longer. They also reflect poor dealer experiences across the board, though these seem to be improving in some areas. As a 'daily' car a McLaren is a risk. When I bought my car I had several McLaren owning mates tell me "NOT THE MCLAREN" as they know I use my cars hard and was considering 600LT/720 (I don't like the look of the 570....but loved the drive).
I love McLaren's, think they are superb but for me it's why I went GT3 over Noble back on 2007. Both epic, both quick, one will start each time I want it to start.