Ignatian discernment has been extremely instrumental for me in my own journey. You make a good point about his inclusion of them in the process, and I think it's important to clarify here the exact nature of how he sees envisions their proper usage.
In order for someone to do a pro-con, Ignatius says they have to be in a state of equilibrium -- like a scale in perfect balance -- where they have no inclination either way. The advantage of a pro-con is that it helps you put things on paper so you see how the state of your options really is; because at times, until we put things out in the open like that, the devil uses the murkiness of the shadows to make some things seem like excellent arguments for or against, when they are really insubstantial. [One of] the decisive moment[s] in my discernment was when I saw my cons for what they were and realized they had no weight.
It's also important to realize that religious life does have some really significant cons -- Lilllabettt mentioned some really important ones to consider. If you go into religious life totally incognizant of these cons, you're going to be in for a really rude awakening. So it's important to have all of these in your scale and weigh them -- in a state of complete openness and equilibrium -- against your heart. As someone in the later stages of discernment, it's been an interesting experience seeing just how desperate the Devil can get to try to dissuade people who have chosen this path. All sorts of things which never even factored into my consideration as cons pop up randomly; "Oh, but if I join religious life, I won't be able to _____!" (Normally it's something super ridiculous l but sometimes its those Tylenol commercials and their really adorable babies, an engagement present for my dad) But then I realize what has been given to me, and what will be given, and I realize how foolish it would be to change it for anything else.
It's also important to note that although I used this to discern into religious life, it goes both ways. Sometimes we may think we have a call to religious life, but the cons against it really do have weight, and the pros, when seen for what they are, are selfishness, pride, misconception, etc. Equilibrium is key though, because if you go looking for the answer to be "x," the evidence for "y" is going to have to be disproportionately compelling to make you change your mind.
But the pros and cons for each person are very individual, so the first step is largely to know yourself and what you truly need to be satisfied and holy.