Said Penney: "To be honest before the game I would have taken a point but obviously we are delighted with the win.
"This is a tough place to come. I've seen Rotherham play live twice and once on TV this season so we knew they were strong defensively.
"We needed something to build on in an away game and we got that with the early goal. We were able to cope with what they threw at us and then we got the important second goal. It killed off the game and we kept another clean sheet."
Disappointed Rotherham manager Mark Robins said :"We had 60 or 70 per cent of the possession but we couldn't open them up and get the ball in the net.
"Obviously we are disappointed to lose our unbeaten record but we knew it was going to be tough. Darlington are a good side and they have spent some money. Darlington showed us the way and what we need to do."
The Quakers went ahead after nine minutes with a cleverly-worked opener that caught Rotherham cold.
Abbott's astute ball found veteran midfielder Juliam Joachim wide on the right and as Rotherham defender Paul Hurst backed off the former Aston Villa star threaded an accurate pass inside for Abbott who provided a cool finish ramming his low shot out of reach of keeper Andy Warrington.
Darlington were forced onto the back foot after the break as Rotherham stepped up the pace looking for a leveller.
Millers boss Robins threw on young striker Marc Newsham for Chris O'Grady and was immediately involved as the home side tried to find a way back.
Newsham set up Andy Todd but his 25-yard shot flew over the bar and when Todd crossed the ball, Newsham's effort was blocked.
But the home side were punished after 76 minutes when Joachim, quiet for much of the second half, burst down the right and picked out Blundell with a pinpoint cross from the right and his firm header left Warrington flapping.