Yes, there are mature IP over FC implementations, BUT it HIGHLY depends on the HBA 
(FC card) and drivers in most cases.

Emulex, Qlogic, LSI and ATTO seem to be the major manufacturers, alas, I have neither 
ATTO nor LSI cards to test/play with. I'll be happy to test one or more of them out if 
someone donates my way. ;)

Windows 2k, XP, 2K3:
Emulex LP800 and up work with a little configuration, (you may need a config util)
 although you want to look closely at the speed displayed by the network adapter. it is
 in MBps NOT Mbps (106 megaBYTES/sec, not megaBITS, and is actually 106.25MBps)

QLogic QLA2200 and up work with the correct driver, although the speed display seems to
be halved IIRC. QLA2100 adapters do NOT support IP in Windows.

Solaris (8 and up): 
Supposedly supports IP over any HBA with Solaris drivers, but I can only confirm 
QLA2200. As of Solaris 8, there were specific QLA2xxx patches, haven't checked on 
Sol 10 yet. Look at the FCIP driver (man page) for more info.

Linux: 
I have absolutely no clue why, but as of 2.6.21 it looks like there is NO kernel 
support for IP over FC. In fact, every drievr changelog I've skimmed over has bits and 
pieces of 'removed IP code' stuff. From what I've read so far, there has been an actual
effort to remove IP over FC from linux kernel code. I've searched the web, and the 
kernel source code (grep -R etc) and haven't found support at this point. 
Emulex claims to offer support with their driver, but changelogs seem to indicate it's 
been removed. I only have one emulex card and it's in a windows box for now, so I haven't 
verified this.
Qlogic offers drivers with IP support for the 23xx (and up?) cards, BUT they've dropped 
support in newer versions of the driver (check the changelog in the newest version for 
"remove IP", also note that the driver will run a 2200 but NOT IP over a 2200)
In Linux, the idea seems to be that 'it doesn't make sense to run IP over your storage 
network' and so it's simply not supported. A rude shock to say the least, considering how
flexible the kernel is in general. I guess if you already have a 5km cable run, you 
should just run another for your IP since 'IP and storage traffic over the same cable 
doesn't make sense'. Sigh.

Dunno about BSD, IRIX has one card by a manufacturer no longer around that supports IP/FC
 with the OEM driver. No clue whether MacOS of any version supports IP/FC, a quick search
 doesn't seem to show aything.

Ok, as for actually setting it up, that's pretty simple. In Windows, it's just another 
Local Arera Connection, however, you will probably want to set up a static IP since it's 
pretty danged unlikey you have an FC router with DHCP compatibility. ;> You can use a 
windows server or a dhcp server program on 'regular' windows if you like.
In linux, it's usually fc0 (1,2, etc) and again, configured pretty much the same way as 
an eth0. Other OS's i don't have enough experience with IP/FC to say for sure.

As with GigE. you will REALLY want to set up a MUCH larger MTU. The largest MTU you want 
to use is 65,280. For file transfers over a good connection, this is nice. For interactive
connections (games, chats, internet etc) you'll wnat domething a lot smaller, say around 
7936 or so as a starting point. (IPv6 can have variable length headers, so I'm leaving a 
little extra room in the MTU size for that)

Gotchas: You've probably got a 'regular' PCI slot. 32 bit, 33MHz, which is 133MBytes per 
second. A 1Gbps (entry level basically) FC card can push 106Mbytes per second. This leaves 
only 27Mbytes/sec for EVERYTHING else on that PCI bus. The most commonly used PCI device 
is...your hard drive. So, one of the two is going to be slowed down. I simplify a bit, but
 them's the facts. ;> 

Feel free to email me if you want more detail or if you think I might be able to help you 
out a bit, I'm not an expert, but I have learned a bit. I'm also very interested in new or
corrected information.

Thanks
paul at note able computers dot com