I'm not quite sure that sticky option would work for Hotmail (http is stateless), since according to OpenBSD's pf faq:
This "sticky connection" will exist as long as there are states that refer to this connection. Once the states expire, so will the sticky connection. Further connections from that host will be redirected to the next web server in the round robin.
I also am still unclear about the status of "sticky" feature, since until recently there were reports of problems, and 148290 is still listed as unresolved in the Current problem reports assigned to freebsd-pf@FreeBSD.org