Andrew,
the choice of editors depends a bit on the state of expansion your QL is in and also a lot on your personal preferences.
For low-end QLs with original CPUs and occasional use, I would recommend the editor that comes with the GST Macro Assembler or other GST languages (available from Dilwyn's site). It is optimized for low memory situations and will run even on unexpanded QLs.
If you like and use the Pointer Environment, QD (Jochen Merz, apparently still commercial) is by far the best editor for that environment. QD is probably the most "modern" editor for the QL. Starting up the PE and QD from floppy disk, however, can be a pain.
If you are familiar with emacs for other platforms, it is also available for the QL - It is not the fastest thing to use, but has a bunch of features and even supports syntax highlighting.
If you want feature-richness, and are fine with remembering a lot of commands, The Editor (DP, now free), is probably the thing to use - It is fast enough compiled SuperBASIC, but a monster of a program memory-wise (It is probably the largest superBASIC program you can build - with line numbers from 1-32767 in steps of one, it is hard to imagine you can build something bigger..., but has a huge amount of features (column mode, even word processing functions, quick find and search,...). Even if written in compiled SuperBASIC, its speed is still impressive. The learning curve, however, might be a bit steep (even if basic commands are somewhat close to ED)
And the last one is my favorite for plain QLs: MasterSpy. Completely written in assembly, it has all the features you might want from an editor, it is fast (especially scrolling and screen updates) and easy to use, as it supports both a command line and popup menus.
On all larger machines I have (Q68, Q40, QXL, and QPC), I tend to use QD, because it is so easy to use. On QLs with suitable memory expansions, I use MasterSpy.
All the mentioned programs except QD can be had from Dilwyn's site.
http://www.dilwyn.me.uk/editview/index.html
Tobias
