Well its nearly time for the Beta and I'm very excited, been reading the press release for the dates and the awesome unlocks you can get for the main game. So I thought I be nice and post it up here if you have not seen it already.

DATES
Bulletstorm Epic Edition will give you one week head start to everyone else, starts next Monday (18th April) and lasts until Sunday 24th Arpil.
Then the normal beta will begin for those who have codes for pre-ordering in advance, start date is Monday 25th April and lasts until Sunday 15th May.
UNLOCKS
There are several unlocks for the beta (these unlocks will pass over to Gears of War 3) with a wide variety of criteria to unlock them.
Flaming HammerburstComplete one match by Sunday 24th April (Exclusive to the Bulletstorm week start)
Flaming LancerComplete one match during the week of 25th April
Flaming Sawed-Off ShotgunComplete one match during the week of 2nd May
Flaming Gnasher ShotgunComplete one match during the week of 9th May
Beta Tester MedalComplete one match during the beta, attaches to you profile in Gears of War 3 and can be shown in the multiplayer lobby.
Thrashball ColeMultiplayer skin unlock, complete 50 matches (any game type) during the beta. There is a catch, you must then complete 10 matches as Thrashball Cole to permanently unlock the character.
Gold-Plated Retro LancerThis is the hardest/longest unlock, complete 90 matches during the beta (any game type) and then score 100 kills with the Lancer to permanently unlock this skin.
So there you have it, the full list and got to say it does look like a lot to do but I'm hoping that the 60 matches for Thrashball Cole will count towards towards the lancer as well (would make life easier). Anyway so give a shout if you going to be on the beta and will have to organise a night to work on some unlocks together and have a laugh.
Source:
Gears of War Official Site