I've got one of Jem's refurbished ones. Had it for over 4 years and done several thousand miles on it. The needle is rock steady, in fact everything works exactly as it should. But I've also had a lot of success by buying cheap old ones on ebay, and rebuilding them myself. They're a bit fiddly with the odometer cogs but it's not that difficult.
If you look for a bog standard 50mph speedo, they go quite often for less than a tenner. You can then stick any face on it you like as, lets face it, the actual speed reading is a work of fiction anyway
If you compare the quality of the internal workings of the original speedo, with the remade ones, you'll see why this isn't a bad idea
I suspect you'll find that Jem only refurbishes original speedos.