Until recently the GMail web interface was simply unmatched. When GMail first shipped, their conversation view was so far ahead of what anyone was doing on the web or in a fat client. I don't try out as many email platforms as I used to, but from what I have seen, it's still the best implementation of conversation view available.
Additionally, you hinted at the other main reason I use GMail in your first bullet point: "Control over your own data means you own it, you have it on your hard disk, it is not on somebody else's storage medium."
Sure, this means Google has access. But it also means I don't have to find a way to make that data accessible to me everywhere I want it to be. I don't have to pay for the storage. It's a solved problem... and available at a great price point ($FREE).
I trust google slightly further than I can throw them, so for now this is an okay deal.
Additionally, you hinted at the other main reason I use GMail in your first bullet point: "Control over your own data means you own it, you have it on your hard disk, it is not on somebody else's storage medium."
Sure, this means Google has access. But it also means I don't have to find a way to make that data accessible to me everywhere I want it to be. I don't have to pay for the storage. It's a solved problem... and available at a great price point ($FREE).
I trust google slightly further than I can throw them, so for now this is an okay deal.