Choon Gan, our membership guy, is normally pretty prompt, but he's a volunteer like the rest of the officers. If it's been longer that you think is reasonable, you might check with your bank to see if your check has cleared (if your membership was paid in that manner).
The application has a note at the bottom to "Please allow up to 6 weeks for delivery." If you're within that time window, I'd say be patient. If it's been longer than that, let us know.