Portrait lens on APS-C

On APS-C, I've been using my 17-55 for portraits for some time. I found it ideal for everything from groups to close up shots of one or two people.

When I had a baby I found the 17-55 too wide though, and bought a sigma 50-150 2.8. This lens is rather large but fantastic, and works well for close ups of children or the classic head shot.