AM or PM?

Well if most of your races are in the morning, try the hard workouts in the morning. If you run like crap in the morning run hard workouts at night.

For most athletes pm is best as mornings can be difficult to get started and motivated. Its a personal thing though.

Elite high mileage guys have to cope with double runs in order to get those killer miles under their belt every week to maintain strength and super charged fitness levels!

For me its not about dedication. I just don't feel good at all when I try to run hard in the mornings. Especially on the sunday long runs. I like to be hydrated, well fed, and mentally prepared before a workout. Not wake up and run out the door.

If you have a choice, I think that doing a main workout in the AM is ideal with only bonus miles in the PM. If you have to cram it into an hour before work, then it's not going to work, though. Pros have the luxury of getting up, eating breakfast, having a cup of coffee, driving to the track, warming up, and starting a workout at 10am. I can't do that, so I prefer to do important workouts at night, when I can devote some real time and energy to them.

the body is stronger later in the day as well!

I love to run in the AM before work.. but with 2 kids I have to run after they are asleep in bed (about 8:30-9PM)

Either way as long as you stay consistant, you body will adjust.