I've got a HP-LP2475W (along with many other people on here) which was never intended by HP to be a 'photo' monitor but it does a bloody good job. Sadly I think it's been discontinued although the closest replacement for it looks interesting (their Z24x) as it has 10-bit colour (and claims 99% Adobe RGB) for which you'll need a suitable video card (typically nVidia Quadro or ATI FireGL) and you should be using displayport connections (as no other supports 10-bit).
I got rid of my desktop workstation years ago - being tied to something that's not portable is so 1990s. All my photo work is done on my 6 year old laptop - as well as everything else computer related.
I'm happy with my HP x2301. It has a low headroom and fits into my recessed work area under a wall cupboard. Colour tuned it on my Spyder and has remained rock steady ever since. It was recommended to me by someone on this site I think.
HP w2408h. Probably discontinued but still gives great results when calibrated. Also use a Samsung SyncMaster S278350 which also give exceptional results when calibrated..although it did take me a little time to figure out that whilst the Spyder2Pro did a good job, I still had to manually adjust the contrast abd luminance to get results that were in sync with my profiled printer. After that, no problem.
One of the monitors on the editing machine is a Sony bought from PC world. I thought that one was pretty good considering and comes up pretty damn close to sRGB when profiled with Spyder Pro 4
Just bought a Chillblast beast though, along with an additional 24" Asus VS247HR Widescreen LED Monitor. Far far superior. In terms of sRGB gamut again it is very similar but the colours are much purer on the screen (I have a twin screen setup with both side by side)
I use three 24" HP-LP2475W monitors in portrait (vertical) mode. Gives me a 47" diagonal desktop, 1920x3600 pixels. Can spread a foto across all three to work on with Canon DPP; Photoshop isn't so well behaved.
Two is easy to set up, and really worth-while, even if you just keep your old one. Three needs a fancy video card like a NVIDIA GeForce GTX 670.
however they don't hold calibration longer than a few days
How thick are they?
All the best ones are noticeably thicker (say 1-1.5" compared to generic LCD screens. It may simply be a case of the thicker ones have better air-circulation & cooling ability therefore more likely to be a more regular temperature (and thus retain calibration).
Also do you leave the monitors on for (say) half an hour before calibrating? (as this allows the temperature of the components to settle and thus colour emission from the screen will have reached a constant level).