The largest problem facing the Palm OS world is satisfying the users who demand color AND room for apps AND long battery life AND simplicity.  The 515 does a pretty good job of balancing these issues and produces a serviceable handheld, but it still falls short for power users.
The 515's color display is a big jump compared to the 505, but only having 160 x 160 pixels really limits the device.  I'm getting older and Palm's shrinking displays are getting tougher to deal with.  The larger display on the Pocket PCs are much easier to deal with.  However, this (and the battery life) is the only real gripe I have with the 515.
With 16mb of RAM on board, it has plently of room for apps and data, so much so that I have never really needed to use the SD expansion.  It runs fast, and does everything one would want a Palm to do.  The Palm OS is still far superior to Pocket PC for contact management, todo lists and appointments but users who are heavily reliant upon Outlook may want to look at the cheaper Pocket PC models (Toshiba especially) as they are still a better fit for Outlook users at almost the same price.
Finally, it seems to me that the battery just doesn't last as long in the 515 as it did in the 505, the price one pays for being able to read the screen.  This is only a minor issue but it can be annoying at times.
The largest problem facing the Palm OS world is satisfying the users who demand color AND room for apps AND long battery life AND simplicity. The 515 does a pretty good job of balancing these issues and produces a serviceable handheld, but it still falls short for power users. The 515's color display is a big jump compared to the 505, but only having 160 x 160 pixels really limits the device. I'm getting older and Palm's shrinking displays are getting tougher to deal with. The larger display on the Pocket PCs are much easier to deal with. However, this (and the battery life) is the only real gripe I have with the 515. With 16mb of RAM on board, it has plently of room for apps and data, so much so that I have never really needed to use the SD expansion. It runs fast, and does everything one would want a Palm to do. The Palm OS is still far superior to Pocket PC for contact management, todo lists and appointments but users who are heavily reliant upon Outlook may want to look at the cheaper Pocket PC models (Toshiba especially) as they are still a better fit for Outlook users at almost the same price. Finally, it seems to me that the battery just doesn't last as long in the 515 as it did in the 505, the price one pays for being able to read the screen. This is only a minor issue but it can be annoying at times.