If you're a serious user you simply can't do without it, and this can be expensive.

Any serious user won't buy their stone.

The ability to create printed copies of diagrams that appear on a computer screen is an essential requirement of many serious users.

He wasn't a serious user, but maybe sometimes he got a little crazy.

Was she a serious user?

Rap sheet as long as your arm, a serious user.

But is it powerful enough for serious users?

The man was a serious user.

This was to be a serious machine, for serious users.

He eventually became a serious user of hand wipes and lotions at the urging of his doctor, an aide said.