I see this thread is a little old, but what the heck?
I just came into possession of a PB 520 (no "c"), and I love it. My first Powerbook was a 5300 (no "c"), and in many ways, I could see where the 520 was nicer than the 5300. It has built-in ethernet, as trag mentioned, and even had a built-in modem! Let me tell you in 1994-5, that was a big deal! As trag mentioned, an ethernet card would set you back $100+, and a modem card would be 100-. Also, having it built-in was nice, as then you could then use the printer/modem port for something else (like hooking your Newton up?). The only knock was that it didn't have the pc-card slot, but that was a wildly new innovation at the time, and you could always upgrade.
The B&W screen is a turn off to some, but it has 8-bit video out...I'm awaiting my video cable to arrive via eBay (drat, I knew I should have hung onto it when I sold my 5300...).
I remember seeing a blow-out sale of a 520c at Office Depot, I thing, in 1996 or so...for the mid-300's. I remember being really tempted, even though I didn't "need" one (I probably needed one back then *more* than I need one now!).
Anyway...I wiped the hard drive clean (wow, 320 MB!), and installed both MS Office 4 and WordPerfect 3.1 (thankfully, it has an 8MB RAM card in it, for a total of 12 MB!). Wow...I remember buying an 8MB RAM card for my 5300 for $200, and being happy I got such a good deal (do you know, those b@st@rds at Apple, sold the 5300 with 8MB of RAM, and then turned the virtual memory on to 12MB? When I went to turn the VM off, I literally could not open *any* applications...talk about underpowered!).
Anyway, I'm looking at using this as just a wordprocessing machine. When I can dig up my AAUI-adaptor, I'll hook it up to my network, and to an external display (I like the B&W for text, but the video is wavy...I'm guessing the video cable is feeling it's age. At least the hinges look strong, although there is more play in them than I would want).
If anybody reads this, please let me know what options there are for replacing the ancient hard drive...