Before I purchased this game, I saw many reviews stating they didn't like the game because it was essentially luck. I wondered why they said this, and bought it anyway. Having put quite a few hours into this game (enough to have almost finished once, plus more) I definitely don't think it's luck based. I also own the board game and believe me the computer based version is much easier (mainly because the rules are about as clear as mud for the board game - playing the PC version actually helped clear up some questions with the board game itself)
Having said all that; the game can be frustrating. Often you fail a quest a few times and you can't see any reason why accept bad luck, but luck doesn't determine the whole game. It's extremely important to pick the right characters and use their abilities to the fullest. For example, Kate the Scientist is immune to terror effects and really this is one of the most useful abilities in the game. Amanda is able to complete multiple tasks per roll, again an amazingly useful ability. Mandy has a built in ability to (once per day) re-roll two glyphs. Very handy. Sister Mary ignores locked glyphs completely. Last but not least in my go to list of characters is Mark who can complete tasks in any order. This can be extremely advantageous when facing several rooms with numbered tasks.
Another way in which this game isn't just luck is the way in which it takes practice. Practice to know when to use a character and when to heal them, and which tasks to give them. Having no prior experience with Elder Signs you can't just pick up this game and be fantastic at it. That would prove it was luck based more than it being difficult I think.
Overall, this game is really good and definitely worth what I paid for it. I'd definitely recommend this game to anyone who doesn't mind being occasionally screwed over, but wouldn't recommend it to people who frustrate easily or want to rage quit a lot. The Elder Signs and the surrounding story is also really interesting, especially for fans of H.P. Lovecraft.