Team 17 did the logical thing and quickly released an official Worms 3D demo. This is a polished playable demo of the game which fixes a variety of issues which came up in both the English and German alpha demo leaks.
The 100 mb alpha demo, is the one MegaGames had the chance to try out at this years ECTS show and came in a 60 mb zip file. The official one is of a similar size and also comes in English and German versions. The demos feature a 2 player deathmatch, with a limited weapon set.