Yes, you are guaranteed the pact. You are not guaranteed a good pact however, and a bad pact at the wrong time can make your life (and your party's) considerably difficult.
There are the occasional complications, yes, but it is still far easier than spending years learning to fling bat poo.
Man this thing was full of outdated stuff. Swoop Falcon I make(made?) avatars! Last updated 12-23-2008. Requests not unwelcome. Last request 01-12-2010.
Avatar by me.