I have never played a lot of IF, I have always been much more interested in the idea of writing some myself, but I though that since I am writing one now I should maybe play a few to see what they are like.
After reading some threads here I decided to start with Wishbringer, and it has been nothing but an infuriating and frustrating experience. It is full of archaic and enormously punishing mechanics and fail-states that more or less force you to restart the game from scratch if you do something wrong at some point during the game. The fact that it's archaic is of course partly because it's almost 30 years old and I understand that.
What I want is something that doesn't stress you out, something where you can't prevent yourself from finishing the game by unwittingly leaving an item in a place that you can't get back to or walking into a room that you are trapped in if you don't have a certain item. Something that is calm and methodical and lets me play at my own pace, without having something chasing me and without dying just because I stood in the same place for 2 or 3 turns. Something that is in concept more like a Lucasarts game if you know what I mean.
Winter Wonderland by Laura Knauth would be another good choice I think. It is a fairly recent old style puzzlefest but with a definite goal to reach. No time limits, as far as I can recall it's impossible to put the game into an unwinnable state and fairly straightforward to map as it's not too sprawling. It's also impossible to kill yourself which is unusual in these types of IF.