Own the disk and store it on your HDD is the best way to go, I was so glad when that feature was made by MS. Always prefer to have a disk just incase
But you still need to keep it in the drive.
I keep big loading games installed, like Fallout 3 and Oblivion and then swap around with whatever game I'm playing hardcore at the time. Like for now I have RE5 on the harddrive, next week it could be Force Unleashed again.
Same thing i do. Also helps prevent the 360 overheating when you are playing the game extensively.
Its possible they are raising the price of the arcade to encourage people to buy the Premium, to get rid of the excess stock prior to discontinuing that SKU. For weeks however, everyone has assumed that they would encourage sales of the Premium by providing great bundle offers. We should have known better with Microsoft, why offer a great deal when you can effectively strongarm the consumer by jacking up the price of the other options.