Besides 2005's Live @ Giants of Grind I haven't really heard much of the crazy Swedes' music prior to Mongo Musicale. The trio clearly likes to goof around and have fun and this wears of. There's nothing too serious about what they do and this can be heard, but it doesn't make the music bad, on the contrary I'd say as the humour adds a lot to the music. But besides the very obvious humoristic touch the music has it doesn't differ much, if anything from most other grindcore.
The band is pretty good at keeping things varied, but the song is of course mostly played at full throttle. The band does gear down or add some silly things that prevent it from being one long same-sounding pummel. Another positive element is that quite a few of the songs clock around the two minutes. This allows the music to be more than just a couple of blastbeats and two riffs. We may not be talking top notch grindcore a la Nasum, Napalm Death or Embalming Theatre, but Birdflesh still have some pretty interesting things going on and they are a good alternative to all the seriousness.
Overall I find Mongo Musicale to be quite entertaining. Sure it's simple and sure it's a bit childish, but it offers a good laugh now and then and that is what counts in the end. So if you got a sense of humour then Mongo Musicale is a recommendable effort.