I'm running a hilly marathon in 5 weeks. The more hills I can do the better so have been doing the Boston ones twice a week. I screwed up the tempo definition. I do my flat course runs along the Charles River, and need to make them tempos.
You can still use hills for tempos if the hills aren't too steep so you don't kill yourself on the downhills.
I've done them both ways - on hills for hilly races (hard to keep the effort up on the steeper downhills, but that can be good downhill training) or on flatter terrain where I want to also keep the legs moving relatively repetitively rather than the variation that hills provide.
I do my tempo runs on a somewhat hilly course, because it's either deal with hills or deal with traffic lights where I typically run. You just have to be willing to adjust your pace somewhat. My pace tended to be about 15 seconds slower than my 'T' pace on the uphills, and about 15 seconds faster on the downhills.
As far as 1-hour race pace... I personally don't think it's a bad description. If you can run a 10K in 50 minutes, or 55, or 1:05, then your tempo pace should probably be in the ballpark of your 10K pace. If your 10K time is faster than an hour, your tempo pace should be a little slower than your 10K pace. If your 10K time is slower than an hour, your tempo pace should be a little faster than your 10K pace. Just based on that (plus possibly a little trial and error) you shoud be able to get it within about 15 seconds of where it should be. I do like your description based on when you start to feel the effects of the effort, though-- that's a new way to think about it and it rings true to me.
No more marathons
Here is my argument about the "pace at which you could race for one hour" description. Raise your hand if you have ever run a 1 hour race. Bueller? Anyone? That's what I thought. Nor am I a big fan of "comfortably hard" as I find that oxymoronic. I prefer the focus on when you start to feel the effects of the effort.
Daniels description of a Tempo is a 20 minute run at your pace you could hold for 60 minutes.
Emphasis added for clarity.
Boston 2014 - a 33 year journey
Lordy, I hope there are tapes.
He's a leaker!