I'd say that YES the blockchain.info wallet would be a great solution for your needs.
For someone with your transaction volume, I think it's a no brainer to use their wallet and make periodic deposits on an exchange.
Edit: What jwzguy said above me is correct. He's just not as verbose as I am.
I think the new method for hacking is this whole social engineering attack... hack into twitter or facebook, get access to my gmail, then lastpass, then find wallet password... But I have the advantage of not being a big target, so its unlikely someone would go to all that trouble!
I am really liking blockchain, I created two wallets, one for online transactions, and one for instore transaction. Downloaded the ipad app, and have it autobackup both to email and dropbox. Password is a 15 character generated password from lastpass.
Wish I knew about them before. But we are back in business accepting coin!
I am also really impressed with Blockchain.info. They've done an excellent job. I just got their Android app and now I feel like I could go to merchants and demonstrate how they could easily accept bitcoin at POS. Their wallet allows you to import from many different backup formats and sync with the satoshi client. It offers many ways to back up your keys, as you mentioned. I just noticed they have a built-in mixing service for anonymous transactions and the nice big green buttons for depositing cash are awesome for showing ease-of-use (although the fees are too high for me personally.)
I only have one complaint so far, and that is that the Android client doesn't seem to have any security. I just got this phone so I'm still figuring it out....I assume there's a way to lock access to certain apps on it. That may be why they don't have any password on the app itself. But until then I can't leave it paired to my main wallet - anyone with access to my phone could steal all my BTC.