Did this at the weekend on the way to Eden Festival. its about 55 miles and goes straight through the borders and into Galloway.
The road surface (once out of Edinburgh) is fantastic, smooth tarmac %90 of the time. The traffic (again once past Penicuik) is not bad, mainly courteous and careful logging trucks. its the tradesmen in small vans you have to look out for.
There is a HUGE climb before you get to Moffat, about 15 miles at least, and i was actually feeling the effects of altitude at one point. However this climb is doubly rewarding. With not only a fabulous decent to look forward too but also one of the most stunning views I've seen in central Scotland. Just over the pass the road opens out at the top of a corrie called 'the beefbowl' and you can see the whole valley all the way to Moffat and beyond spread out before you. I nearly cried.
There are several nice stopping points, Organic Farm shop near LaMancha and a lovely cafe in Broughton, but be warned after Broughton there is nothing till Moffat, so pack a sandwich.
In conclusion a great ride, take a tent, make a weekend of it. Prolly better for cyclists who have had some experience and looking to get their mileage up, like me!
Was thinking of cycling to Lynkilee festival this weekend, or DIY Knockengorric at the end of the month, anyone up for them? (knock i think is a two day affair, at least for me!)