I would get unreliable readings about where studs started and stopped. Even with tape horizontal and marking the positions it'd still be a "general area" of a stud. Ended up with a few extra holes because of it.

I cheaped out on stud finders for a long time before I finally just paid for a proper, well functioning one. I like the Franklin ProSensor that "highlights" a stud with a row of LED's. I'd also recommend a few rolls of blue painters tape to help mark out studs and hanging locations that are easily removed when you're done.