So I've just started playing KSP2 since For Science! came out, and one of my biggest annoyances so far has been the maneuver nodes. Many times so far I have had to reload a quicksave because I, despite following the timer on the node as best as possible, have way overshot it, sometimes to the order of hundreds of meters per second. Initially it confused me as to why this was happening, for in KSP1 I am a very accurate burn-starter and stopper, but after some examination I think I know why: when you plan a maneuver, the game calculates the burn time based on the current max acceleration of your craft; using the max acceleration and the deltaV, it does some simple dimensional analysis to find out what that time should be (ex. 10.0 m/s2 max, 800.0 m/s deltaV, burn for 80 seconds). Now, this system is quite simple and effective if your mass doesn't change, say for small burns where it for all intents and purposes the mass is a constant, but once you start burning a significant percentage of the fuel of a craft, it can start to cause problems. Acceleration is force divided by mass, so if your mass is cut in half then you will accelerate twice as quickly, but (from what I can tell) the game doesn't take this into account. Therefore, because the burn time is seemingly only calculated when you make a maneuver node, you get situations where you end up burning far above the deltaV of your maneuver if you trust and follow the tools provided by the game.
So, how should the devs fix this? Well, they could implement some complex dynamic calculation where it takes in to account how much mass you'll lose over the course of a burn and accounts for it in the burn time, but this would still be susceptible to errors if you, say, throttle down near the end of a burn to be more precise. Or, they could have the game recalculate the burn time across the course of a burn, constantly recalculating it based on the changes in your acceleration (which I believe is done in KSP1, though that may be a mod that I use). OR, and this is by far the most radical suggestion, they could just reimplement the deltaV based system used in KSP1. That way, you could actually tell how close you are to the desired orbit, regardless of however fast you accelerate. Like, if for some reason you want to use RCS, or not use full throttle, or you want to do anything that is not exactly in the vanilla, proscribed method of doing things. Isn't this game supposed to be about being creative? about not following the rules? This is by far the biggest design issue (in my opinion) of the game so far: a single-minded, rigid approach which the devs think is the best is the only way of doing so many things, from the topic of this post, to not being able to even plan a maneuver past your max deltaV (also susceptible to calculation errors), to the timewarp limitations, is hard built into the mechanisms of the game. Hopefully, though, these artificial restrictions that stifle the spirit of KSP are seen as what they are -- restrictions to creativity and fun -- and are removed so that this game can reach to and beyond the heights of KSP1.
(I'm sorry if this seemed negative, I really do like so much of the game and have been really impressed playing it so far.)