My sparring partner does, and he does it quite well. Just don't make that your only option, it can be countered very easy.
[ame]http://www.youtube.com/watch?v=MWbYhbDwwCM[/ame] I am actually getting better at it day after day.
Only on the inside, I always try to counter the liverpunch with a right hand, and uppercuts are good if he's really close.
I only really ever throw one when people are bulldogging me and leaning forward. I do a digging uppercut type punch to the body though regularly when inside. Sparring partners hate it.
Countering does not work guys, none of the great HW champs were counterpunchers.... hit first, hit last.
When i slip to the outside of a jab on orthodox fighters i do it... I slip, and leave my front foot in place but take a half step back w/ my back foot. then step in and come with a right uppercut to lead off my counter combination. I throw the straight right out of that slip as well, or bring the uppercut down to the body