Brilliant, just brilliant. I think that ends this debate. Revan is an unknown.
I agree. And for as much information as possible, it should stay that way.
On a related note my head-canon for Revan has always been thus:
Revan mastered both sides of the Force as a result of ascending to mastery first as Darth Revan, then as amnesiac Revan. However, when he regained his memories (and mastery), it came at a terrible cost. Revan's duality has resulted in serious mental instability (which we see in SWTOR's flashpoints) which gives him dark side leanings, and a lack of personal control. He may be a master of the techniques, but he has a lot of difficulty applying it in any meaningful way.
As for his tactical abilties, he was never anywhere near Thrawn's level, but was very good at a few things that make him look way better than he really was. He was a good leader, who delegated relevant responsibilities to those who could best handle the. He was ruthless, sacrificing worlds to take whole sectors. And finally, he played the long game. He had a goal, and he pushed towards it. G0-T0 noted that Revan consistently fought the Republic while preserving its infrastructure. If he wins, he controls a mighty Republic backed up by the Star Forge. If he loses, the Republic is now united, wary of invasion, and still has a military industrial complex intact.
As for using both sides of the Force at the same time, I do agree with the fact that it shouldn't be possible (considering they both require opposite mental states), and that it is much more likely that he achieved oneness with the Force, expressing it in its purest form. The description was pretty similar to Jacen's experience. I think the problem most people have is with the "twin rivers" description, but that could have simply been a description applied by fallible witnesses who didn't understand what they were seeing. A unified Force expression could in fact feel that way to someone trained to think of it that way.
But that's the great thing about head-canon. H-canon is always going to be above G-canon from a personal perspective, and Revan just happens to be a lot more moldable than the average Star Wars character.