*** Unreleased ***
Removed the Potential 2 and 3 traits
Now make Potential 1 = 25% exp bonus.
That would make it a clear non-brainer first choice......
Based on the experience numbers for champions, +25% experience taken at level 3 only pays for itself at level 12 (i.e., at the point when you'd normally have gained enough experience to be level 12, you'd actually be at level 13). This is not a significant advantage, nor is it so much better than the other choices you could have that you absolutely must take it before anything else. Granted, you will reach some levels slightly sooner than you would otherwise, but you won't be a full level ahead until you'd normally have reached level 12.
You also don't get a second "free" level until some time after level 20 (I don't know exactly when since I don't have experience numbers for levels after level 22).
Being level 13 when you'd normally be level 12 is such a minor advantage that I'd seriously doubt the utility of taking Potential - an extra 1 to 4 health (depending on race and class) and an extra 1 or 2 accuracy, dodge, spell resistance, and spell mastery isn't going to make much of a difference to you at that point.
This is, however, still better than what Potential I currently is, which doesn't pay off until level 20, or the subsequent Potential traits, which don't pay off until your champion would normally be level 18 (Potential I and II) or 17 (Potential I, II, and III). Mix them with Knowledge and that stays at about level 17.
Edit: Assuming my curvefit is correct, Potential 1 as it currently is will not give you a second extra level (read: the first extra trait you earn, once you account for taking Potential instead of something else) until you'd normally have reached level 41. Thus, in a normal game the only benefit you'd see from taking the Potential trait is that you would have 1 extra level and 1 trait that grants no direct benefit to anything. This isn't a good pick currently for anyone. Taking all three potential traits and/or knowledge is useful if you're getting large bonuses from leveling (mage with Flame Dart, or the lightning bow, or something like that), since you at least get a few extra levels before you'd stop, but only 1 extra level by the time the map runs out of experience (or by when you run into the level ceiling, assuming you've tried making a superhero) isn't worth it.
Even at +25% experience, you only get your second extra level when your champion would normally be level 25.