Don't own one but seriously considered one. The frame comes with the brakes, they are not sold separately so the price is pretty good. Low trail thin walled tubing hand made in Oregon at Zen Fabrications. Low bottom bracket, typical rando geometry. I am not a fan of tig welded bikes so I bought a Rivendell instead.

My guess is the Rambler is a much more comfortable bike to ride than the Riv.

Would I compare it to a custom? No, the beauty with the Ocean Air is you can buy one today and not wait for a custom bike to be built. Second the custom is going to cost more and if you are just experimenting this would be a good choice. The Cycle Toussaint and Velo Orange and not even in the same category and their price reflects this.

The Rambler gets great reviews and I have yet to see one on the second hand market which should tell you something. Check out the Google 650 group and do a search I am pretty sure there are a few owners there.