I really loved TW1's pacing. Each chapter usually started slow from some small event that gave you the general idea of your goal and set you on your way, after which you were free to go about your business and explore at your own pace, getting to know the important people and picking up pieces here and there, until it all came together and culminated in an intense finale. Each chapter was in a way a story of its own and the pacing reflected that, with a patient (but certainly not boring) build-up to each major event. Even the side quests were usually nicely connected to the main story in some way, as they often explored similar themes or introduced you to characters that would play an important part later on. I can't really think of another game with a similar pacing, but it worked incredibly well, all the way up to the very satisfying epilogue.
TW2 failed in this on many levels, as its chapters (especially the first two) started with long, linear sequences that basically just served as info dumps and introduced you to pretty much every important character in that chapter right away, as well as every problem you were required to solve. Then you had the middle part, where all exploration and side questing took place but the actual story moved forward very little. After you had finished the checklist the game gave you, the game put you on rails again and lead you to the conclusion of that chapter. Only the second act somewhat managed to capture that adventuring feel of TW1, although it too was very straightforward overall and only felt different because if gave you more than one or two threads to follow. TW3 fortunately has much better pacing and structure again, although the questlines are still nowhere near as complex as in some parts of TW1, and aside from Velen it doesn't always seem quite sure what each storyline is supposed to be about and what themes it wants to explore.
As for Infinitron's criticism about TW1, it's hard to even comment on it because it so weird. The storylines of Act II and III aren't difficult to follow at all. You try to gain access to the swamp tower because you think it's a way to catch Azar Javed, who has been your target from the start (whether he's tricking you or you're tricking him is up to you). The only somewhat strange thing about it is how the focus of the investigation suddenly shifts from the initial attack to the murder, although, like
Sensuki said, the quest is more about finding someone associated with Salamandra than it is about solving some particular mystery. Act III introduces you to the big players in Vizima that will play an important role in the second half of the game, and even though there is some intrigue involved, the chapter isn't "supposed to be" anything else than it is. It's one of the most straightforward chapters in the game that finishes up one storyline and offers some foreshadowing for the next, sort of a transition between the early game where Geralt's mostly tracking down Salamandra by himself and the late game where things start to unravel and the stakes get notably higher.
