afp over wireless lan extremely slow
Radio interference? How many other wifi spots are nearby? How many are using the same channel as you? Does this only happen with AFP or does it happen with other protocols as well (e.g., HTTP, CIFS, etc)? Are you using A/B/G/N?

What's the memory usage look like on both systems? Is one (or both) maxed out? The traffic seems very bursty. This could indicate that one or both sides can't buffer the stream properly (i.e., not enough free memory).

Do you have the same problems when configured to use an Ad Hoc network? If not then the problem is your WAP.