You should be able to create accurate sketches in Inventor very easily and quickly if required. We need the ability to sketch accurately first up without having constraints and dimensions automatically applied and clogging things up. Why can't Inventor have a switch to turn off the automatic parameters and allow you to free sketch quickly and accurately like you can in AutoCAD?
If you want to quickly draw up something fairly accurately and quickly you always have to work with automatic dimensions and constraints. We should also be able to draw a line at an exact angle and distance without the padlock appearing on dimensions you enter locking them down. Sometimes you just need this ability such as when designing something new you may want to quickly sketch up something just to see if it would be ok, you may delete it several minutes later so you don't want to waste time locking everything down.
There should be more freedom to sketch properly first up. I do realise that you need dimensions and constraints eventually but you just don't have the artistic freedom to quickly draw up an accurate sketch and then add dimensions and constraints later.
Sometimes sketches are so insignificant, they don't need dimensions and constraints limiting the user. They could remain as unconstrained sketches. You wouldn't bother placing dimensions and constraints on them. Objects you don't really care about and knew you would never need to edit at any time.