I personally prefer a "modular concept" for portable devices.
1. The core device in my ideal setup is a small, pocketable flip-phone with BT, 2G or faster data, a small color screen, mini keyboard, a 1MP or greater camera for candid shots, SD slot and Palm OS for PIM (addresses, phone numbers, calendering). Stereo headphone jack and a good music player with songs stored on a large SD card.
2. A Bluetooth GPS and BT headset.
3. Add a larger media-centric (gaming, video, music, ebooks, audio books etc) tablet PDA with gaming controls, a built-in microdrive (or a CF slot for one), BT, WIFI, dual expansion (one CF and one SDIO), again running Palm OS, a 4 inch VGA display, and USB Hosting. Keep your music library, audiobooks, ebooks and all your important data on the Micro HDD. Transfer songs/playlists back and forth between this device and the phone. Use this as a portable HDD when connected to a computer and easily transfer files back and forth. Hook up your digital camera (#5?) using USB hosting to transfer, store and view pictures on the large screen.
4. A BT keyboard and mouse added to #3 for a laptop replacement.
#1 and #3 would be able to synchronize their data automatically. Mix and match as the situation dictates. Running out to the store to grab some milk or out for a run and want to listen to some music? Grab #1. Heading out on a 2-5 day business trip? Take everything and still carry less than a laptop. Use #3 during the flight or down-time for gaming and entertainment (TV shows, movies). In a Wifi hotspot at a coffee shop? Grab #2, 3 & 4 to catch up on email and make VOIP calls using Skype, where your incoming calls are automatically forwarded when #1 is off or set to voicemail.
Modular and flexible. #1 and #3 have some overlap, but not much. I don't want a phone that's too big to stick in a pocket, and I don't want a gaming device or PDA with a screen that's too small for movies, ebooks, and games.
Convergence is good up to a point: Jack of all trades, master of none with too many compromises.
This modular concept would require a lot of cross-device and cross-application integration, but it could be possible with the right combination of applications and OS support (disclaimer: I'm not a developer). Maybe Palm OS on Linux will help make my dream come true

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Brian