Rough estimate for storage space is 1MB for every 1 minute of 128kbps MP3 or a bit under 30 seconds for 320kbps. So roughly 4 hours of music would fit on a 256MB player using 128kbps MP3's.
I've owned an iFP-895 for a few months and run quite a few miles a week with it. I've had no problems at all with the construction of the player. It still looks and performs like it's brand new, though I do keep it in the armband sleave at all times which adds negligible weight and size. The player itself is excellent and I would highly recommend it. The only complaints I have is that software is a bit clunky, the player requires drivers to be recognized (not recognized as a driverless USB storage device), and the armband that is bundled with it is a piece of garbage. I don't understand the armband thing since IRiver sells a good one on their site, which they should bundle instead, guess they are just trying to swindle a couple extra dollars out of people. I've never heard of any quality problems with IRiver flash players, so the fact that franguinho has had the same problem twice would make me think he is unintentionally doing something unusual to cause the failures.
I owned a Creative Nomad II before the IRiver and was quite happy with it as well. One of the most resilient electronic devices I've ever owned. I must have dropped the thing 20 times or more before it finally submitted to the abuse and died on me, and even then it didn't completely die, it still works, but for some reason can't read or read to media beyond about 10MB, which made it rather useless. If you plan to use the player during rigorous activities I would not recommend anything but flash players. You can't go wrong with Creative or IRiver, both have good audio quality and sturdy construction. I went with IRiver because of a better feature list including OGG support which was a must for me. Battery life for the IRiver is phenomenal as well. I don't know if the spec sheet claim of 40 hours is accurate, but it's pretty close if it isn't.