Android App store warns you that you are about to start a large download via 3G and asks if you're sure you want to do so. Personally I find that a much better approach. Apple doesn't know the details of my contract and if I want to download 70 (or 170)MB over 3G, surely that's my prerogative and why should my phone stop me?
I have unlimited 3G data plan on my iPad and it always hated that Apple won't let me update some apps until I'm near WiFi spot... until I bought Galaxy Nexus inserted SIM from my phone with limited data plan and it exceeded my capped data plan in the first hour (OS updates).
