Okay, just two quick questions:
1. Merlin Pro comes in 2 versions, and can run under DOS 3.3 or ProDOS. Are there any reasons why you'd want to use one or the other (besides the fact ProDOS supports subdirectories, etc.)? What are the pros and cons?
2. What's the difference between Merlin Pro and standard Merlin-8?
You might also consider running the cross assembler version of Merlin on a modern computer and then copying the files to your disk image for use in an emulator or with real hardware using some kind of flash media device.
A cross assembler running on a modern platform gets rid of some of the limitations of running the assembler on an Apple II... basically infinite memory and much faster assemble times.
I use the cross assembler that I wrote on Linux, but a lot of people use Merlin.
True, there are annoying limitations to running it on real hardware (and if I do anything serious I'll probably cross-assemble), but I want to experience doing all of it on the real hardware. That said, I'd like to have the least annoying time doing so, hence me asking what's what so I don't wind up painting myself into a corner later down the road :)