Is all that worth saving ~$23?
quick answer, no it's not. I have one with the bigger sd card holder, and it works fine. but my goal is to have my project working with both types of ethernet shields. when I upload my finished code to the internet, I want people to be able to download it and use it with either shield without trouble.
I think I'm close to having a compatibility layer I can use, but I'm having trouble with the packets. the library does some complex stuff in the packetloop_icmp_tcp function. I can get my code to show that it is getting packets, but I can't get it to detect the right kind of packet so I can grab the data from it.
edit: it would even help if I knew how to properly debug the library. there's some kind of debugging built into it, but I don't have a clue how to use it. UDR0? I was taking a guess that it's some internal name for the serial port, but it doesn't send anything to the usb serial port. swapping that code out for Serial.print() just gives errors that it hasn't been defined yet.