Rio KarmaThe good was the clickable thumbwheel, via which
almost every function on the player could be accessed, coupled with the comfortable way that it sat in the hand.
The good was also the excellent, intuitive and feature-rich firmware with good codec (i.e, Vorbis) support.
The good was making it natively networkable via the dock, allowing it to be used as a networked music drive.
The bad was the harware fragility, both the thumbwheel and the hard drive.
The bad was also the PC-side synch application which was flaky and didn't allow drag-and-drop access to the drive. The network client wasn't the best, either.
There was no ugly. I still haven't found a player as downright ergonomically excellent as the Karma. The Sansa comes a poor second, even when used upside-down, as I do.
Sansa e200The good is the small, lightweight form factor (hurrah for flash-based players)
In common with the iPod nano, the good is also the scrollwheel. I find it a really intuitive and quick way to navigate menus.
An easily user-replaceable battery is also something that should be mandatory.
The bad is portrait-style screens. I feel DAPs benefit most from a landscape style, in order to better accomodate album and track titles without scrolling.
The bad is also placement of the scrollwheel. I find it really uncomfortable to use with one hand, as the player sits high in the hand and feels as if it's about to fall out. See above for (partial) solution. This also applies four-fold for the heavier, larger Gigabeat, I could just not get along with that player.
Basically, for me, the majority of my handheld gadget likes and dislikes come down to ergonomics and their effect upon the interface (in its widest possible sense). I had an old Nokia mobile with a monochrome screen which could be read without a backlight and needed one button to access most things. Now I have a new Nokia that came with my job that I detest; I have to move my thumb from button to button to achieve the simplest task and their effective interface design seems to have disappeared

* bascule goes off in a huff about poor physical interface design on multi-functional gadgets...