It is, honestly, not nearly as bad as you'd think. The weight should be pretty well distributed, armor doesn't have to be all that heavy to stop a sword, and the gambeson is doing a lot of the heavy lifting for piercing weapons. Blunt weapons, well, those are going to be unpleasant pretty much no matter what. You get really hot though; there's a reason that the Saracens did such a number on the crusaders when they were able to get them outside of cities.

Wearing a plate carrier is, IMO, worse than wearing a gambeson and chain maille.

I read an interesting article about historical armor fights. Basically some researchers got special forces members to wear replica historical armor and simulate battle as described in various surviving epics and identified the armor to be surprisingly effective