I think the idea that Emerald is unstable stems from the fact that people are told that it's unstable in tutorials for Fire Red or Ruby. I'll admit I was once part of that ignorance that it was unstable. I guess people think it's unstable because of when they try to use a program with it, the program uses different pointers for different versions and therefore messes up the ROM.
Yeah unfortunately people think it's unstable because, well, they think it's unstable. I think we need to somehow abolish that rumor. Hacking Emerald only causes problems when you overwrite existing data, as far as I know, or somehow mess with things too much.
I didn't realize there was so much space on Emerald. How much larger are the secondary tilesets? And I was also unaware of all the music choices. I'll have to experiment with Emerald. ^_^
Oh yeah, you gotta at least give it a try. The music is amazing! It gives you so much more freedom and it also helps in scripts because there's a track to go along with pretty much every situation you can think of^^
The thing with the tilesets is that the primary tileset is smaller but all of the secondary tilesets are larger. For me, personally, this is great because I always find I'm running out of room in the secondary tilesets. Not only that, you also get more blocks as well (as opposed to tiles) which is great for lots of block edits. Also, the primary indoors tileset (Tileset 20? Or is it 12? I'm not sure) is empty (except for a few PCs and random items) and all the palettes are blank as well. All indoor maps in R/S/E use the secondary tileset for all of their tiles/blocks, which gives you the option of filling the primary tileset with whatever you want!
Another thing: Emerald also comes along with all of the benefits of Ruby & Sapphire, including RTC (giving you the option of a Day/Night system), berries, Pokénav,
tons more OWs, the list goes on and on. Be careful when you're experimenting with it though. It's very easy to get hooked ^^
Ooh, I forgot! And whenever you enter a town/route/city/underwater or whatever, the box that the name is displayed in changes, depending on the location!
More stuff: R/S/E tilesets hold up 512 tiles and can accommodate up to 512 blocks as well (512 == 0x1FF by the way).