Some thoughts on using the Gnutella network
It sucks bandwidth As mentioned above, the simple act of connecting to a gnutella network* will eat up a fair portion of your bandwidth. Add to this the seemingingly instantaenous downloading of your obscure files by many many people, and it becomes apparent that this is not an application for a dial-up internet connection. While you can restrict the bandwidth a downloading user takes from you, that's not enough if you are on the end of a modem as your websurfing and other net activities are now slow as heck.
It's hard to find anything other than popular stuff If you're after a zipped copy of Photoshop 6 or an illegal copy of a Britney Spears song, then fine. If you're searching for a video of Peter Gabriel in concert, or a high quality picture of mountains then you are out of luck, because...
You can only search on filenames Gnutella doesn't support any kind of metadata in it's searches. So, just like E2 where you can only search on a node's title, not it's contents, with gnutella you are relying on the file sharer to provide you with a verbose and meaningful filename. This also leaves the system open to abuse; I searched for "Photoshop" and while most of the results returned were Photoshop-specific, I also had results like "anime video japanese lolita chugakusei school sex preteen porn cute hentai rape girls idol asian avi mov windows photoshop traffic .mpg" returned to me. Another problem with filename only searching is that, using mp3s as an example, unless the sharer includes the bitrate in the filename, you cannot search based on that attribute.
Downloads often fail It's been my experience on Napster that downloads will fail about 50% of the time. On Gnutella, I've found download failures to happen more like 90% of the time.
It's not anonymous As mentioned above, your IP address is there for everyone to see, making it a haven for wannabe hackers.
* I say "a" gnutella network here, because there is no single network, as there is with napster.