IMO PA armor should have PA training, but not need that to wear it. PA should come with reasonable default settings that only those with training can intelligently alter. This would mean that PA should give slightly better bonuses to a trained operator, and that only a trained operator could access its advanced features ~if any (including a targeting computer; alternate vision modes ~or pipboy link).
Optionally: A trained operator should not need to haul the suit on his back when not wearing it (being trained, they know how to set it to auto, and can pull it along behind them ~even pack stuff in/on it).
Any machine like that could stand without falling. Push it from behind and it steps forward to stop its fall. In game... the armor should look and function like a dumb, non-combat NPC that follows you around.
PA should increase strength to a flat minimum (due to it doing the lifting ~a +2 bonus makes no sense as the armor would be just as strong with weak PC as a strong PC); however, PC's that are stronger than the armor should get no bonus at all, and in fact suffer a strength decrease, down to the strength of the armor (Say an 8) ~not only that, but the armor could even have a variable strength maximum for different work environments (something that only a trained operator could change) ~meaning you could find an armor that LIMITS your strength to 6 unless you know how to change it, and/or the password to enter maintenance mode.
PA's should degrade fast (faster without PA training), and only trained personnel can run diagnostics, and do basic maintenance (without which the armors benefits degrade with condition ~accuracy, strength, and protection). Even a modern day color-copier needs tuning after a week of use, imagine robotic power armor.
In Fallout 1, the moment you put on your suit of power armor (which admittedly was tough to get), the game was basically over. NOTHING could touch you. There were hardly any drawbacks to wearing Power Armor in FO1 and 2 that I can recall.
IMO this is how it should be; the armor was designed to make a man immune to smallarms fire ~a walking tank. There should have been a kind of Buckshot heavy pistol for PA'd infantry that they could shoot with abandon to "clean" off clinging enemies with no chance at harming other PA'd troops (like if ambushed in a dark building). I would say yes to the armor having some drawbacks (like -80 to sneak and lock pick), but they should not have 'nerfed' into a "Power Armor" costume, as opposed to the real thing.
In FO2 Jacob was said to have fought Marcus for several days (HtH?). PA should make you feel near invulnerable (while it works).