Yes, Nightsky, there has been substantial discussion about SDM elsewhere on the forum of late, see for example the thread I started about my 20" order in the Equipment Discussions. Several IIS folk have placed orders.
The main cost of a large dob is the mirror. You are looking at $5,000+ for a quality large mirror alone.
I have done all of the maths, and when comparing with the cost of freight from the US (would have been $US1400 in my case), plus customs, I have saved about $2,000 by ordering from Peter Read (SDM). You should also bear in mind the extras you get from Peter that Obsession and others don't include. For example, Peter supplied a high quality focuser ( I am getting a Moolite focuser), cases for the upper case and poles, and a shroud, all without charge, and you would pay extra for all of these from OS.
So, what are you waiting for........
no worries if anything goes wrong.
what I paid then, you would buy a decent scope here at todays prices, add to that the import duty,they charged me 35% and it took a few years after many letters to the customs dept to get a refund as it should have been 25% for a telescope and 35% for a camera, I have looked through a few 20" scopes and you won't be dissapointed 
