Here's another simulator to add to the list on the first post
It's a recently made BMS Player called "forgetalia", and it's designed in the style of the beatmania I series.
I've tried it with a few songs, and this sim's really good I think, if one doesn't mind the current limitations.
Here's a quick list of what I've noticed...
The good:
- It supports WAV, MP3, and OGG sound files
- It uses the BM I 'classic' layout (Blue notes on the line. Easy for me to use

)
- Both player 1 and 2 have right-side-scratch (following in the BM I style, and again, it's good for me

)
- It starts up fast, no caching required, just put song folders in the 'BMS' folder
- It has a variable hi-speed using 1 and 2 keys.
- It can display a BMS song's readme.txt right on the screen. Convenient!
- It supports the full set of BMS #WAV and #BMP commands (from 01 to ZZ)
The not-so-good:
- The judgement timing is absolutely brutal! As in, '80 bads and 20 poors on a song I can normally full-combo'.
- When playing songs with a large amount of notes, the groove meter won't increase much (Similar to Rhythm-It).
- Requires a powerful computer (I got 47 FPS from it on my computer)
- It's a little lacking in features currently (but that's understandable since it's new)
I still recommend trying it though. Its home page is here:
ttp://cerebralmuddystream.hp.infoseek.co.jp/forgetalia/prot.html