iPhone: No EDGE while you're on the phone

Here's a little lapse in functionality we just discovered on our iPhone that's also documented in Apple Knowledge Base article #305711: EDGE data access is not available while you're talking on the phone. This is standard among most EDGE-enabled phones, but it means that putting a conversation on hold while you're looking up a place to eat -- as demonstrated so nicely by Steve Jobs and Phil Schiller during the iPhone's introduction -- is only possible when connected to a Wi-Fi network.