I've never used my 9mm cylinder, don't have any other 9mm firearms so I've never gotten around to buying the ammo. I reload, and all of my other wheel guns are 38 or 357. I bought my Blackhawk years ago, used, when there wasn't really a price difference.
I do intend to have the 9mm cylinder converted someday to a wildcat round. I stumbled across Gary Reeder who converts the 9mm to his 356grn round. The cylinder is bored out to accept 41 mag brass, the 41mag is necked down for a 357 bullet. Velocities can top 2000fps.
The Blackhawk is a great revolver...and it's built like tank.