I've never used the Dymo, but have extensive experience with both the Epson and Primera solutions. The Epson has really superb print quality (if anything, it may even be BETTER than the Primera, and it's certainly equal) for the price; but it is an INCREDIBLE pain to use. You have to line up a tray with the disk on it very carefully, then insert it in the printer to exactly the right depth (it's possible to over-insert - this is not a "shove it in until it stops" operation). If you get it right, the printer ingests it and prints one disk. To get a second disk, repeat the whole operation. The advantages to the Epson are that the printer is cheap (you'll break trays and feed gears fairly quickly, and the tray is NOT an easily found replacement part, so it's good that the machine is cheap, although it would be much better if it were sturdy instead), the print quality is good, and the ink is reasonably priced.
The Primera is exactly the opposite - it is a beautifully made, easy to use piece of machinery that loads up to 25 disks at once. On the other hand, its print quality is good, but certainly not superb for a $1000+ printer. Not only is the PRINTER overpriced, but the ink is as well - the cartridges are a black and a tricolor (in the Bravo II model I've used), and the color cartridge only lasts about 30-40 disks (for $40). Annoyingly, Primera has chipped the cartridges so that standard (much cheaper) Lexmark cartridges won't work in it. The Primera is basically a standard Lexmark engine attached to some custom feeder hardware, and sold for six times the price of the Lexmark inkjet it's based on. The feeder hardware is very well built, and the most sensitive part of the print engine is the heads (which are in the cartridges, so they get replaced all the time), so I don't worry too much about any cheaply made Lexmark parts breaking down (and the Lexmark parts may not be from a cheap consumer inkjet anyway - Lexmark may make parts specifically for this sort of use (another example would be label printers used heavily by UPS, FedEx, etc...)). The only serious issue with the Primera is the price of the printer and the inks. The chipped ink is annoying, and Primera tries to stop you from refilling the cartridges by remembering the serial numbers of the last few cartridges used, so you need to have a bunch of cartridges if you are going to refill. This shows that the overpriced ink is a VERY deliberate business decision.
If you have more than a few disks to print per month (especially if you print more than one or two of the same design at a time), swallow your anger at the price and buy a Primera (even though it is truly overpriced, as opposed to something like a Nikon D3x, which is EXPENSIVE, but not actually overpriced - the D3x offers performance commensurate with its price, while the Primera (and especially its ink, where they admit to selling $20 ink for $40 and putting a chip in to force you to buy it) is overpriced because there is no alternative and they can get away with it). If you print in low volumes and have the time to mess with the Epson's inane feeding system, stick with the cheap Epsons for a far better price/performance ratio.
-Dan
