I recently switched from working 12 rep sets to 6 rep sets and have noticed that I am not as fatigued as I used to be postworkout. I don't think I am failing to push myself as the last 2 reps are difficult to pump through in each set. Nowadays, about ten minutes after my workout I feel completely fine, but I would feel a burn if I attempted more of the same exercises. With my previous workouts I would find even lifting a pint of milk in the fridge would be felt in the arms and sometimes even sleepy. Would do you feel post workout? Any comments?

I do a lot of conditioning exercise to push threw fatigue. Sometimes after leaving the gym I am dead. Other days I feel like I could train harder when I am finished. For me it has a lot to do with how much sleep I have been getting and my diet. If I eat right and have enough rest I can push myself otherwise its hard.

For me it depends what type of workout I am doing and what body part. When I was exercising to failure I would be more drained after a work out and many times had to lay down and rest to try to recuperate some strength to move around. Now that I'm doing more of a strength routine and not going to failure, or at least not on all of my lifts, after a work out I'm a little shakey but this goes away fast and within an hour or so I feel I could do the whole workout again ... but don't as that would defeat the purpose. Now when I work my legs ... or I should say when I "could" work my legs ... in either strength or going to failure I am drained regardless. Working the legs just takes more out of me.

The fatigue that you are used to is just residual lactic acid build up, it doesnt really relate to the depth of muscle stimulation involved in your workout.

I used to do giant supersets of 20 rep breathing squat and deep stretch dumbell pullover for 12 reps- both to failure.

8 supersets and i was seeing stars, and had to scoot down the stairs of the gym on my butt. i have to say that the burn, pump and general 'zap' that gave me was always more intense than regular 6-8 rep squat or leg press ever did, even when pushing some respectable weights, yet even with the different percieved recovery rates, I improved mass on both systems.
As long as you give your all no matter which rep range you work to, you will see results. Take the quicker recovery as a bonus, not a negative effect

Cord hit the nail on the head.
Try working your routine around so that your failure is your last rep of your last set if you are doing heavy sets. For instance my last rep on my last set of almost anything im screaming and my arms/legs are shaking. If you are just breezing through your 6 rep sets, change it up a bit or add more weight.