Custom fit
I believe if you fit well on standard sized frames then there is not much need, sure as someone pionted out you can get a custom frame for the price of some high end frames, but, they would not be like for like. You may get a custom 853 main tube frame customed for £1000 but you can buy a state of the art XC carbon frame of the shelf for that that or less.
I think if you can do it, ie: afford it then go for it. As mentioned it would probably save you money in the long run as you would keep it forever.
My Merckx corsa extra is a custom build, in as much as it was not a standard size and was ordered as a custom but it was only seat tube and top tube, all angles and lengths were scaled down from the standard models. I suppose without this it wouldnt be a corsa extra or handle like a corsa extra. The dealer informed me that they didnt make G.I. Joe size as standard :roll:
I will be keeping it forever, as I realised a while back when I thought to sell it. It was listed as a custom size and was a bit dearer than standard but I feel its my special corsa.
I have heard mixed things regarding British builders since being here, builds are ussually great, for a small minority its the attitude that seems a bit off. One guy who has built my wheels, preped my Merckx etc and a couple of friends have his frames is Eddison cycles in Clowne. A great guy who will help with any problem big or small. His frames are real quality.
Thats my two cents/pence.
Whatever you ride, enjoy.
Jamie