Gmail's biggest advantage is sheer number of users, not the actual technology. Their filtering would be pretty effective if all they did was learn from their users hitting the spam button.
If you get a spam into your inbox, chances are that hundreds or maybe thousands of other gmail users read that message before you and marked it as spam. After a certain number of these manual filtering events, Gmail can simply blow it out of all other mailboxes.
I usually manage to sell the concept of contributing as a future compatibility issue. If you make a one-off change and don't get it merged back, your company is going to be the one supporting that change in the future.
If you can get it merged, there is a very good chance that you will be able to deploy future versions without modifications.
I would definitely buy a 10 inch iTouch. But please, no keyboard! If I wanted a keyboard, I would use a netbook.
For me, a quarter inch think glass encased touch LCD with wifi would be just perfect for surfing on the couch.
Apple web apps to store the HTML/CSS/Javascript on the device. It's called a cache.
You can also access iPhone specific stuff from javascript. They provide a series of javascript objects that allow you to access the address book, save a native database, etc.