I'm not really missing out because:
1) I don't drive, so GPS would be of no use to me.
2) I very rarely use emails to communicate with people, just IM/text/call, so emails wouldn't matter.
3) I don't use my phone enough for a contract to be worthwhile, and last time I looked 3G/mobile internet is a massive rip-off on PAYG, plus I can't think of a situation where i've needed, or even wanted internet access when i'm out.
I don't really get why having an all-in-one device is so important? The iPod Touch is very slim and it's the perfect size to fit in the pocket, and as I have more than one pocket, I can easily carry more than one device...
But yes, I agree with the last point, with most things you get what you pay for...