I've got the WRT54G (with the Sveasoft firmware) running in bridge mode to a Buffalo (WGR54 or something) just fine. Granted, it was a pain to set up, but it's working.
Patrick, I have exactly this setup, and have some problem, so I'm hoping you can help.
Linksys WRT54G w/Sveasoft Satori-4.0 v2.07.1.7sv firmware (192.168.xxx.1)
Mac mini hardwired to the router (192.168.xxx.18), OS 10.3.9, NFS shares setup through NFS Manager, and SMB shares setup with SharePoints and Windows File Sharing is turned on. OS X firewall is currently off.
Buffalo WBR-G54 (192.168.xxx.2) in WDS bridge mode connected to the router w/WEP 128 security running.
ReplayTV hardwired to the Buffalo, working fine for months, able to stream High Quality files from DVArchive on the Mac mini.
XBox (modded XBMC) hardwired to the Buffalo, streaming fine for months.
PB hardwired to the Buffalo, having problems seeing any shares, but getting a Dhcpd IP assigned to the PB MAC address. (192.168.xxx.19 The IP address correctly shows up on the PB GUI, and I can telnet into it.)
If I hardwire the PB directly into the Linksys router, I can see SMB shares from the Mac mini, and even mount NFS shares through the telnet interface. But, when I move it back to the Buffalo client near the tv, it won't see shares. The Add Account button is greyed out, and if I try to mount an NFS share using the exact same commands that work when it is plugged in the Linksys router, I get
# mkdir /mnt/smb/nfs
# mkdir /mnt/smb/nfs/iTunes
# mount -t nfs 192.168.xxx.18:/Users/xxx/Music/iTunes /mnt/smb/nfs/iTunes
mount: 192.168.xxx.18:/Users/xxx/Music/iTunes failed, reason given by server: Permission denied
mount: nfsmount failed: Bad file descriptor
mount: Mounting 192.168.xxx.18:/Users/xxx/Music/iTunes on /mnt/smb/nfs/iTunes failed: Invalid argument
"xxx" indicates edited content.
The fact that you got this setup working gives me some hope.