Second time lucky. Well, technically speaking, third. After replacement of the Proline DM1945MP3 narrowed its flaws down to design rather than dodgy lasers, I got a hassle-free refund from Comet and walked fifty metres over to Currys to try a Packard Bell alternative...
A little more expensive (the OP3 is £35 with a charger included, the OP4 £30 without and the OP5 £40 with charger and WMA functionality) so I opted for the OP4 with a £5 Uniross power adapter. This was because the OP4 is entirely opaque plastic and you can't tell by sight whether you've left a CD in. I know myself well enough to recognise transparent lid sections as a useful feature rather than tackiness.
I haven't tested the included in-ear headphones, but they do look very cheap... a little disappointing for a player which was apparently about £60 around a year ago. I'll try them out before I sign this off. After a quick setup I found the player has perfectly functional directory navigation, of the type the guy I approached in Currys on Monday confidently assured me it probably didn't have. So, in comparison with the Proline—which would have been a wonderful device if either I tried actually bloody worked—how does it measure up?
Cons: there's no dynamic equalisation settings, nor any tone control. Just a bass 'enhancement' switch (which is redundant if you're using proper speakers, and probably sounds as godawful through anything else too.) Volume control is handled via a dial on the side of the player, rather than having extra buttons with the rest on top of the player. Not necessarily a negative—buttons wear out quicker than dials, and dials hold their setting between sessions—but a little tricky to fine-tune, and more susceptible to being knocked in transit. Unlike the Proline there's no built-in battery charger.
General comments: sound quality is fairly average—again, not worth the original asking price of £60, and not as balanced as the DM1934MP3. You can tell that Packard Bell make computer peripherals because the signal emphasis is slightly towards the treble and bass. Slightly more mid-range would have been appreciated. Slightly more output, too—the OP4 doesn't have quite the same amount of raw power of the kind required to keep large passive speakers happy. Whilst listening at maximum you may find yourself wishing for a little more flexibility to turn up a quiet recording or go completely nuts for a few minutes with a loud one.
Plus points: anti-shock, reading ahead and caching of MP3s are all well-handled. Seeking inside and between tracks is easy and fluid, and can be done as the unit is fetching other data. VBR MP3s are handled very well—as are MP3s in general—with quick scan times allowing the disc to rest and conserve power. You can leave it on pause, go off to do other things and expect no skipping when you eventually hit 'play' again. The Currys website estimates up to 9 hours battery life, so a good strategy would probably be to take it out with one or two pairs of rechargeable AA batteries and a couple of regular AAs of a kind rated for high-power devices. Should get you through a travelling weekend, anyway.
I'm still annoyed about the DM1945MP3 design flaw (see that review for full details.) However, the PB-OP4 at its current price is a good substitute. Fewer features and more money—but for someone who likes always to have the background noise of albums they know every second of, reliability and a lack of tantrums from their hardware count.
Addendum: the earphones are acceptable with bass boost on, but seem very treble-heavy. You'll almost certainly want to replace if you intend on a lot of private listening.