It does pick up a bit once you're out of the snow region, more side missions/random encounters etc.
But it is obviously a fairly slow game anyway, particularly compared to GTA. Suppose it depends what you like. The scenery and attention to detail is breathtaking. I quite enjoyed taking my time getting around, just taking it all in. The soundtrack is phenomenal too. Not just the music but the sound effects (wind, insects chirping etc), well worth playing with headphones on for the full immersive experience.
The action, when it comes (and it's certainly not scarce) I'd argue has more of an impact because of the peaceful bits in-between. The characters are great and it's good storytelling.
A game to take your time over and take it all in. Which of course isn't going to be for everyone, but I think it's an incredible game. Just a shame, as per their recent business model, Rockstar are more bothered about online stuff than single player DLC.