I use a Brother 9800PCN, which is USB or network only with no built-in keyboard interface. I love some of it's features, like half cut which only cuts through the label and not the backing paper, as well as the fact that the print resolution is 4x that of the normal PT printers and everything looks a whole lot better. Printing on 1.5" wide label tape is nice too. The price on them is a little crazy, but used/NOS ones go for a reasonable price on Ebay all the time. P950NW is the new version, but I don't have any experience with them.
Since it's PC based I can do pretty much anything I want on a label, including a lot of things you can't do on the all-in-one models. Different fonts/sizes, underline or bold on specific words, and layouts with images that would otherwise be impossible. I use a lot of templates with tables to get the correct spacing on rack panels, and auto-numbering is often very useful too.
It's true that the labels don't stay on cables very well though. I've solve this problem by putting clear heat shrink over the labels, but obviously that's not always practical.
