Wha??? Windows, me??? No reason to get nasty!
But really, thanks LOTR, that helps some. I've been a good LW sharer, Mac only, for years. Yes I can upload, though apparently it's pretty rare that anybody actually wants any of my stuff.

I see that I do have UPnP enabled.

I'm already using my junk filter same way as you describe. Seems to work OK. It's not very smart but I wouldn't call it a dumb-*** either. BTW I'm hesitant to block hosts; I don't suppose you know any way to tell the difference between hosts that are spammers only, and hosts who are legit citizens who happen to have dl'd a spam file and are inadvertantly sharing it?

I didn't know "many OSX users don't even bother with their firewall being on", though I am familiar w/ the conventional wisdom that Macs are safe from bad guys. I just tend to play it safe when swimming in unclear waters; you know what happens when one assumes...

Re your point that configuring firewall only allows LW access: are you saying bad guys--if there were any out there preying on macs--would not be able to use that access for their nefarious schemes?

What is NAT? Can you recommend a post or page that 'splains this stuff a little further--NAT, ports, forwarding, etc.--for dummies?

Hmm, I found out a little more info. My ISP's connection analyzer tells me my modem, while NAT-capable, is in a mode that uses "IP passthrough", which I interpret to mean it is not using NAT [right?]. Does that mean the modem's firewall is not in the chain? My ISP's tech support lady says my modem doesn't even have a firewall but she doesn't sound very expert. In my Mac I have the Gnu/LW port open. In LW I have UPnP enabled and my listening port is in the recommended range. But I still have the brick wall icon in LW. I have not tried port forwarding yet. My IP address is dynamic, and they tell me it'd cost me $ to get a static IP.

Could my modem's firewall be what LW is sensing despite NAT being bypassed?

I can search and find, and can upload and download at good speed. As mentioned before my only complaint is poorer search results than I remember in days of yore. Is there any sense among the Gnutella community that there might be fewer folks on the network these days compared to, say, a few years ago?