A lot of people wax lyrical on the benefit of these. My question is whether a stock frame that has variations from a custom fit such as 1cm out in top-tube and 1 degree slacker in seat-tube and head-tube is as good as needs be for the average road-rider?

Put it another way, at what point is pursuing custom not worth it?

Thanks.

If you're an average sized person with averaged sized arms and legs, you should be able to find a stock frame that fits you well. Custom built frames become more interesting for very short or very tall people.