I thought long and hard about which case to buy for my Zen. It does need one, the screen is very vulnerable. I eventually came down to this one and I have no reason to think it was a mistake. A case must protect the unit from bad weather, bumps, scratches etc all the while being fully functional inside it. This case fits all those criteria.
It's snug fitting rubber which matches up perfectly with all the USB / headphones / power on / SD slot etc. The buttons are perfectly responsive under the rubber too. The tighter fitting, the less space it has to move, the more shock the rubber dissipates while keeping the unit inside undamaged.
Some people think it makes the Zen look tacky, I look at it differently. It's designed to be used outdoors, often in low light conditions like huddling under a street lamp waiting for a bus. Having the bold icons makes it easier to see them.
The screen protector does require patience to fit properly and it is more or less a one-shot-deal. It is a little larger than the screen but that's so the edges fit under the rubber case providing better protection against the rain. The clip feels decent too, and considering the weight of any mp3 player is negligible it should last forever, barring any strain like someone pulling at it too often.
In short, this is a fantastic case which others may not have seen the reasoning to some of the design choices. It's much better and cheaper than the official Creative cases.