Alan I think the pedigree is very important, but therein lies the danger of making sentimental decisions, because "with his pedigree he is bound to be good" In reality very few bull calves can really make an improvement to the general breed and thus should be allowed to multiply their genes.
On a more practical note, at two months old a bullcalf looks very similar to what he will look like at two years old. Obviously secondary sex characteristics still need to develope and he could develope various problems in the remaining 22 months, but the two month rule will be a very good indication of potential. Just don't look at 5 months old, otherwise you will cull everyone ;-)
I cull at birth, those that were too large, no pigment, bad disposition on dam, etc. At weaning the bottom gets culled again and then after puberty for bad scrotums, poor heads, disposition, etc. The best will be sold at a production sale and the few others directly off the farm for those "I need a bull yesterday" cases.