For those that are using Macs, the most logical choice would be to use iPods as your digital audio player (DAP). Well, what if you don't want to use iPods? You can always use any DAPs that are USB Mass Storage compliant (meaning can be connected to any modern OS without needing additional driver/software), and doesn't require a special software to transfer music (eg. pure drag-n-drop). Example of this kind of DAPs* are most cheapo flash players, Creative flash players, Sony NWZ series, PSP, rockbox enabled DAP, etc. Using these DAPs are easy, since they will show up on Finder just like an external drive/memory card. Drag-n-drop your music, and you're done. Easy right? But what if your library is managed by iTunes, and you already have a perfectly auto-cycling smart playlist? Transferring these tracks manually won't update their tags (last played, and playcount). What to do?
Apple scripts to the rescue. I found this website that hosts many kinds of Apple scripts for specific situations. There's one that will add a specified number to the playcount tag on selected tracks (called Add or subtract Play Count), and there's one that will update the last played tag of selected tracks to a specified date (New Last Played Date). Perfect! :)
So how do use these scripts? If you follow the readme included with every scripts, there will be a script menu shown in iTunes. First step is to create a smart playlist that you'll use. Then disable Live Updating (important, especially if the criteria for the smart playlist depend on the playcount and last played tags). If you don't, since we're going to apply the scripts in 2 steps, the set of tracks will already be different the moment you use 1 of the 2 scripts. Next is to run those 2 scripts (in my case, I set to add +1 to the playcount, and set the last played to today's date). You're free to drag-n-drop the tracks to your DAP. The next time you want to transfer fresh tracks, simply enable live updating and iTunes will refresh the smart playlist with new tracks according to the criteria.
Of course, the beauty of iPods are their automatic syncing. There another Apple script based utility called iTunemywalkman. It basically syncs a/multiple iTunes playlist(s) to a UMS device. I tried it, and it delete my ratings on the tracks. Weird, so user beware. For now, manually copying the tracks have to suffice for me. I'm sure somebody can/already created Apple scripts to automate the whole process.
So there you go. You can use your choice of DAPs, and still use iTunes' powerful smart playlist feature.
*Note that iPods are not these kind of DAPs (unless you use rockbox) because even though it is a UMS device, it requires iTunes (or 3rd party software) to transfer music.
**Note: Of course, non-iPod DAPs will not be able to play iTunes DRMed tracks. Simple put a criteria not to include tracks with Protected kind in the smart playlist. iTunes+ tracks (non-DRMed AAC) will play fine on any AAC supporting DAPs.