I've had a go with this type of software and it's a poison chalice.
You probably want to use it if your music-reading's poor and you feel
that the machine's going to do it quicker.  Maybe it will, but then
you can't correct the inevitable errors!  You may not even spot them
and think you've done a decent job, but I can assure you that many
musicians will spot the tiniest errors with unerring ease and will
delight in telling everybody else even if they don't tell you.

What I found was that where the music did somewhat sloppy things, the
scanned result was badly wrong.  For instance, a pop tune that simply
merged two musical lines mid-bar caused the software to try keeping its
beat count correct by shifting half of the next bar, so the musical
lines were totally garbled and needed heavy editing.

On more 'proper' but complex music it also added errors, such as missing
a change of clef in the middle of a bar, misreading note values and
then simply omitting the bits that over-ran the bar line, putting the
wrong adjacent notes into trills, incorrect interpretation of octave
shifts -- you name it.  Result: many hours of hunt-the-error fun.

I'm quite happy to believe that there's better scan-to-MIDI software
than the cheapo stuff I tried.  However, seeing that OCR'ing plain
English text with well-respected software seems to throw up numerous
daft errors in what appears to be perfectly-readable print, one has
to have realistic (i.e., low) expectations of its musical cousins,
with all the additional interpretation that music needs.

You certainly should only try it if you have well-printed and clean
original music to scan, not a photocopy or low-resolution over-compressed
scan image.  Also, only even think of trying if you have a decent
sight-reading friend who can point out the errors.  And, of course,
much sheet music is rather big so you may well need a large-format
scanner as well!

Julian Dyer