Its not just email that the notification area is useful for, messages, voicemail, missed calls or whatever information a third party app might want to show. I've had the temperature up there for example.

I would often forget to reply to a message or such like on iOS because I was in the middle of doing something else when it came in and once the notification banner had dissapeared it became victim to "out of sight, out of mind".

Tethering on iOS was dependant on your service provider, some allow it, some don't. Some allow you to add it for a fee and my network allows me to do it but because they're a virtual network they don't have their own carrier profile so although permitted on the tariff, you couldn't actually do it because of the parent carrier profile forbidding it.

Eco system, well I don't think anybody could deny that there are a lot more higher quality apps on the apple app store, however, I've not found that I've wanted or missed anything that I had on my iPhone.

Adrian