They work but they have a limited range of tuning, basically canned maps and nothing more.
For filter and slip ons it will help but it might not be right on for the combination.
Personally I think it's better to get a TTS Mastertune or SESPT or Powercommander V
where you can make specific changes to help the tune, and if you grow into cams, larger cyl, bigger intake, gear changes, etc you can make those changes.
If you get a VH and it can't keep up with the changes you have to get rid
of it and buy the TTS or SESPET etc down the roadanyway...
"My rule of life prescribed as an absolutely sacred rite smoking cigars and also the drinking of alcohol before, after and if need be during all meals and in the intervals between them." Winston Churchill