MobArena spawnUnit

I'm working on a project making it possible to create mobArena's without any mods/plugins. Already created a few devices, the most important: the spawnUnit. This device will allow you to spawn up to 5 different mobs (0-5 of each) and fully give you control over the amount. This way you are able to create wave setups for an arena fight. In the schematic link you will find one spawnUnit, you can stack them up/left/right and create even more possibilities!

More MobArena stuff coming soon!
MobArena V0.1: http://www.planetminecraft.com/project/mobarena-v01-a-real-arena-fight-for-spsmp-configurable-no-mods-or-plugins-needed/
MobArena V0.2: http://www.planetminecraft.com/project/mobarena-v02-fully-configurable-spawning-behavior-your-arena-waves-no-modsplugins/
ATTENTION: this arena needs mobs being able to spawn with dispensers. This is currently only available in the 1.2 snapshots. I hope MC updates soon, but in the mean time you'll have to download the snapshot version here:http://assets.minecraft.net/12w04a/minecraft.jar
(http://www.minecraftwiki.net/wiki/Version_history/Development_versions#12w04a)
navigate to: %appdata%/.minecraft/bin and replace the minecraft.jar file with the downloaded one. the map has to be unpacked in %appdata%/.mincraft/saves.
Feedback: I would really apprieciate any feedback here in the comments. If you liked this map, leaving a diamond will make others to find it and enjoy too =)

Zipron