Interesting video of two types of 15th century armor, and the men in them demonstrating their agility and various fighting styles.
I had the impression that armor basically turned you into a lumbering tank, rather than much of a warrior. But this seems to not be the case...
I can add a few things about chainmail on that note. Hardly an 'expert' opinion, but I was given an opportunity to walk around in one for almost two full days by a friend from historical reenactment society for Days of Czersk.
1. They make almost no noise, even if you are running in one.
2. Despite weighing even ten kilogrammes (especially the ones that go past your belt and/or have sleeves) they don't throw you off-balance and the mass of all that grab is almost unnoticeable. That said, after taking it off I felt much lighter that I suspected I would be.
3. They act almost like heat-sinks on a hot day. I was sweating less in chainmail and tunic than in t-shirt and jeans on a sunny summer day.