Um, to me there's nothing special about Federer's technique. It's a pretty straight forward semi-western style forehand with the moderate loop take back and often times windshield wiper finish.
Really, his technique on all his shots is pretty straight forward and simple actually. What distinguishes Federer is not some mystical and totally ideosyncratic technique, but rather his footwork and speed which are so exceptional, his ability to read the direction of your shots that are Hingis like, and his timing when taking the ball on the rise which is Rios like. Basically, it's almost impossible to get Federer totally out of position. As such, he executes high quality shots from all positions of the court. He also mixes in a variety of spins, paces, and angles to keep you off balance and hence this is why opponents are often leaning the wrong way when he hits.
But as far as his technique? Really, it's pretty common these days. It's just that Federer is very smooth and elegant, perhaps that is what you are confusing with "different" technique.
"Different" technique is Bruguera's forehand, which was incredibly ideosyncratic. There's not a single western forehand grip that is hit the way he did. The western grip forehands you see are the more typical windshield wiper style finish a la Moya and Ferrero and Berastagui and Courier. Federer's forehand is actually a very similar motion, only difference being that his grip isn't as extreme. Bruguera's forehand was not just open stance, but completely open stance basically. He also had an inordinate amount of "flop" or wristiness to his shot, and finally unlike other western grips he really didn't have a windshield wiper follow-through but instead finished over his head or above his shoulder with garnish.
Also, the thing is, these ideosnycracsies in my opinion are a bit irrelevant. Once the racket makes contact with your frame, your "finish" is irrelevant. It's where your contact point is that makes the "impact." A lower angle = more topspin. Meet the ball more in front and at the edge = angle. Meet the ball square = flat. For me the "buggy whip" finish Sampras' incorporates feels very natural, but it does not in and of itself do anything. I can hit the same shot doing the buggy whip finish, a traditional above and across the shoulder finish, and a windshield wiper finish. The difference is more so in comfort level. The buggy whip finish feels very natural and I feel gives you a better recovery rhythm for the next shot as it gets your feet squared away more quickly. Doesn't it actually add anything to your shots though? No.
It's just personal preference and whatever feels more natural to you in my opinion. As long as your contact points remain solid, "bad shots" simply are not possible. Try it sometime. Next time just freeze your racket after contact and you'll still be able to hit a good shot. One-handed backhand players prove this all the time. Sometimes they may just kind of stop their finish a la McEnroe (also Edberg did this a lot), and they'll still hit a solid shot. They can also hit a flourishing finish as well, and they'll also hit a solid shot. Where the "finish" comes into play is in personal comfort level. Look at Tommy Robredo. He is an extreme example of someone who really exaggerates his finish on all his backhands. Does it add anything? No. But it is kind of a sub-conscious cue to himself to make sure he sweeps through the contact zone in time. In other words, it gets him to accelerate his swing so he doesn't end up hitting the ball on his heels or make poor or tentative contact with the ball...which with the one-hander as we often know IS the kiss of death.