Once you have a legitimate source of these files, here is how your practice routine transforms:
PG Music sells a legal, supported, updateable version called the "RealTracks & RealDrums Set 1: RealBooks Package." band in a box real books 13000 tunes link
1. "Garbage In, Garbage Out" (Copyright Issues) It is important to understand that PG Music does not own the copyright to the songs. They license the mechanism to display them. Consequently, they cannot ship these files with the melodies written out (due to copyright restrictions on the notes/heads). Once you have a legitimate source of these
2. Computer-Generated Errors While 90% of the tunes are accurate to the standard changes, there are occasional errors. You might find a chord labeled as "Cmaj7" when the standard harmonic analysis suggests "C6," or occasionally a wrong chord in a bridge. These are usually based on specific editions of fake books, so if your band plays a different version, you will have to edit the chart. band in a box real books 13000 tunes link
3. Visual Presentation If you print these out to hand to a pianist or bassist, they will look like a computer printout, not a published piece of sheet music. It lacks the polished layout of a Hal Leonard book.