Kuroyume -- if the Karma is the only player you will be using, and you intend to take it with you everywhere, you might experience some problems. Some people would have it lock up while they were walking down the street listening to it. Some people had very few problems (and some people were better than others at do-it-yourself technical fixes). I think the situation is made complicated by the age of the built-in battery (as mentioned above) and the non-existence of Rio as an ongoing company for factory support/repair/replacement.
This is a good opportunity, if you can afford it, to grab a "relic" of a recent (but at the same time, it seems long ago) era. I think of the Karma as being like a classic Rolls-Royce luxury car -- not really essential or practical, currently, but used in certain ways, a great thing to own and use.
I might say that, if you use the Karma around home, and use a "replaceable," relatively inexpensive flash player while on the go, you will get the most out of your Karma, all things considered. And there is a lot to be gotten out of it.
Don't get me wrong -- I've had a Karma two and a half years, and it's still a very impressive device ... but I think it might be a risky choice as a portable "only player." I'm sure I'm paranoid, but I don't take it anywhere ... which of course in many ways defeats the purpose of having a portable player. But to me, it has never seemed all that portable, based on the interesting threads on the "riovolution" site and based on the availability of more easily pocketed flash players.
I'm not the type who needs to have thousands of songs with me at all times ... in my case, having hundreds is usually enough. Your case is likely different, so base your decision on what your needs are. I hope you get something you like.
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Sources (in order of purchase):
2nd Generation 10GB iPod for Windows (retired)
Creative Muvo 256MB
Creative Muvo 1GB (out on loan)
Rio Carbon 5GB
Cowon iAudio 5 1GB (out on loan)
Rio Karma 20GB (low-mileage collector’s item)
Creative Zen Nano 1GB
Samsung YP-U2 512MB (out on short-term loan)
4th Generation 40GB iPod (monochrome; used as home jukebox)
2nd Generation iPod Nano 4GB
Creative Zen Stone 1GB
iRiver T60 2GB
