A few years ago, I noticed this causing problems on corporate Windows PCs too - not network booting, just getting IP addresses on start up. WinXP on its own was fine with this - would fail to get an IP initially, and so would not be able to log on to the Domain, but shortly after (race condition) would get the IP, connect to the Domain, and just in time for the user to login. But with any services running under a Domain service account (eg on a server) these would always fail during boot and need to be manually started. But it did bugger up GPO processing on XP machines.
But it was specifically associated with one of Broadcom's earlier Gb NICs only on all our PCs and Servers. Must have just been a bit slow coming up, with knock on effects to the port starting to forward after STP. DisableDHCPMediaSense worked for PCs until Portfast could be turned on - even that caused problems with users connecting switches at their desk and then accidentally looping them!
Either way, to this day I see this with most Broadcom NICs. I guess if PXE times out before the port goes to forwarding, this will always happen unless portfast is turned on, and a slow NIC makes it worse. Come to think of it, I think forwarding without portfast takes 50 seconds, doesn't it? If so, I assume PXE would definitely timeout beforehand and that mandates portforwarding. Maybe a Wiki article?