The missions are going all shooting gallery, having me kill 50 guys each time, usually without any real reason for it, no consequences for it, and not particularly satisfying shooting involved with it. For example, at about 25% in, you're in bed with this West guy as he sells his elixir crap, the crowd turns on him for being a conman and you flee with him as the entire town gives chase, and you murder the entire population of the town as you're protecting him. This guy who just fell into your lap as part of the storyline and makes very little sense that Marsten is dealing with him at all.
The characters I'm forced to interact with on these vaguely relevant story missions are incredibly annoying. Sharply downhill after the Bonnie missions. And lately it's all of these characters droning on and on and dragging things out while Marsten whines and makes hollow threats. It cheapens him, and it's not interesting in the least.
Using fast travel more and more, now, since riding a horse through vast expanses of desert is nowhere near as interesting as, say, weaving through traffic.
Losing interest fast.