Now, MMO-Champion has a screenshot from a player experimenting with the new potion on the PTR. As Drysc mentioned, each time it proc'd he got one of the following elixir buffs: Major Agility, Fel Strength, and Major Armor (same as Major Defense Elixir.) The tester also mentioned that the proc rate was "quite high."
Personally, I'm not a fan of random buffs. I like to know what I'm going to get so I can plan my strategy around it. What about our Alchemists out there? Is this your cup of tea or another foul brew to be poured down the nearest drain?