When my last company stumbled into Inventor from Autocad, it was rough... but only for about a week! We used Autocad when Inventor slowed us too much (it was a very fast paced job shop) but after a week, Inventor was the thing, for me.
That's excluding repeat jobs where it was suitable to just reprint or, if needed, slightly modify a Autocad DWG and go from there. There's learning new software, and then there's reinventing the wheel, but they don't have to be the same. Inventor comes with Autocad and a way to download Mechanical Desktop for free.