Yes I found it bit heavy going myself. I would assume symplistically the more intense / vigorous the work out then the greater the EPOC.
The other thing I am wondering about is intensity v duration. For part of my workout I am currently doing 6 x 1 min sprints (11km/hr) up a 4% incline on the treadmill. However, is this better than say 12 mins at 6.5km/hr.