I use FCEUX constantly because it has a good debugger, nice native Windows interface, and easy to use AVI and screenshot capture capabilities.
I sometimes use Nestopia to play games. It has no debugger, but it does vsync better than FCEUX (so it's better for fullscreen, no debuggin; i.e. when I just want to play).
Less frequently I use Nintendulator for very specific debugging purposes that FCEUX is inadequate for (e.g. very accurate render timing, OAM inspection).
I've tried puNES, and I mostly like its interface, but I think it still feels "unfinished".
Probably the big reason I don't switch to other emulators is that the main two (FCEUX/Nestopia) both do the job really well already. I don't even know why I'd
want to try other ones, because I don't know of any need to. They're both old and well known and pretty robust.
I've given you feedback in the past about it, but I'll give it another try right now and take notes...
Okay, here's some honest suggestions based on my experience the last few minutes:
- No drag and drop, so I have to go hunting through directories with a non-native file dialog.
- File dialog does not hide files that are not NES ROMs.
- Alt + Enter does not switch to fullscreen.
- No obvious option for fullscreen in the menu. "Misc > Video resolution > Fullscreen options..." is greyed out?
- When to "Video resolution > Set..." and it gave me a pre-emptive warning, and then after choosing a fullscreen option it crashed badly.
- No debugger, not even something like nametable or PPU tile viewer. Just a couple of minimal memory dumpers?
- Doesn't remember last used directory when I close. Gotta navigate to my ROMs again with terrible allegro dialogs...
- Went to "C:\Users\rainwarrior\My Documents" and no contents appeared, not even a "..\" to back out- dialog is now stuck here. Have to cancel and start again.
- Most of my ROMs are under "My Documents" so this is a problem.
- NSF player has a visualizer but doesn't tell me the track number, or any information (title/artist/copyright) from the NSF.
- Found setting "Save last accessed folder as main." This should be on by default.
- Allegro GUI is very small and hard to read. Blue background colour scheme is uncomfortable to my eyes.
- Small allegro GUI is also hard to click on, smaller than normal Windows fonts.
- Accidentally pressed number keys looking for the default inputs, ended up changing a bunch of graphical settings and now it looks terrible and I don't know how to revert my settings.
- Had to delete my INI file to get back normal looking graphics.
So... it seems to run games fine. I don't have any initial thoughts about accuracy, and really that's not part of my decision not to use it. Here's my top two reasons for not using RockNES:
1. No debugger. This is one of the most common things I want to do with an NES emulator.
2. No fullscreen. If I'm not debugging, I want to play in fullscreen. If I can't do this, the emulator is useless. (Maybe just ditch Allegro if its fullscreen doesn't work?)
Until one of those two things changes, I wouldn't have any desire to use your emulator except to just to test it. Even if it could do one of those two things, though, the other nitpicks make it an unappealing choice compared to other emulators. Sorry if this is harsh, but it seemed like an honest question, and like you wanted an honest answer.
Open source is another reason that I completely left out, here, cause it's not exactly a "usability" issue, and probably a lot of people don't care about it, but I do very much appreciate open source programs, and it's one of the reasons I use FCEUX. I actually modify FCEUX sometimes, and contribute to the project.