I think a lot of people's frustration with this game may stem from the fact that they're trying to play the single player campaign the same way they did Warband, but you absolutely cannot. You will die in short order if you try to be the heroic knight charging into a horde of enemies with a lance and shield.
I can see how this would be frustrating if that's the sort of play style you've come to love and expect from M&B games (and who can fault anyone for that, as the first two games were exactly this), but personally I enjoy the new dynamic guns and grenades add. It makes commanding your troops actually have some meaning, unlike Warband where all you had to do to win most battles was send Swadian Knights crashing into whatever opponents you came across.
For those of you on the fence, I'd recommend making a character heavy in cha/int to boost your leadership and persuasion. It allows you to do some of the more lucrative quests relatively early, and you can earn a massive amount of cash fairly quickly by trading between the Swedes and the Khanate (Swedes want spices and velvet, Khans want furs) which then allows you to buy the best armor, afford a large army, and upgrade them to plate mail wearing musketeers who can snipe enemy armies from hundreds of yards off (Just make sure you give them pistols instead of rifles - much faster reload and the range/accuracy difference is negligible)
