"Ninety percent of everything is crap." http://en.wikipedia.org/wiki/Sturgeon's_law

Not only true for products. I use this rough estimate in developing ideas and prototyping. It works for me.

Just out of curiosity... How many implementations of Arc has pg tried in the past howevermany years?

I don't think any language was written on the first try. Nonetheless, eleven is a pretty amazing number.