I'm a computer graphics programmer, age about 40, based in the UK. I have been using Ogg Vorbis files for ages as my ripped-audio-format-of-choice. I'm not really a fan of closed formats, software patents, and non-free software.
At home, I use Amarok under Linux. I had tried a number of different media players up until then, but Amarok just works and does what I want it to do, unobtrusively and efficiently.
At work, I am forced to use Microsoft Media Player, since no other players are approved for use under Windows (I would prefer to use Winamp). The OGG codecs for Media Player seem rather buggy, although to be fair many of my old OGG files do not pass when run through ogginfo, as they have missing end-of-stream tags.
I have a Samsung YP-U1 and it's pretty good. So much so that it's difficult to get it back from my wife at the moment. Update: I bought another one.
In October 2005 I bought a Yakumo Hypersound Car, which, to put it mildly, was terrible. To put it less mildly, this is the single most annoyingly bad product I have ever bought. Here is a link to my archive of a thread on the Yakumo forum which explains why. While not being outright dead-on-arrival, there seems to be no basic function on this device which does not have an annoying glitch, fault or flaw. Each of these individually are just not enough to warrant a return, but gradually they all just add up to a truly miserable user experience.
I have been searching around for a replacement for a while and, thanks to my wife and a trip to LIDL, I now have a Silvercrest KH2380 installed. I have tested it with some Q5-encoded music files and it seems fine at that rate. Most importantly, compared to the Yakumo, it's marvellous - no glitches so far. It even has excellent radio reception. Not bad for £50.