Perhaps perk was the wrong word, with he talents being called perks now. Replace "perks" with "bonuses" in my first comment.

In Cata, you help level the guild, and this builds your rep with the guild, which dictates what you can buy, like every other rep. These bonuses include heirloom, mounts, and recipes, from earlier Blizzard posts. "And" is important, not to sound condescending but because I keep seeing it used.

Other posts have stated that you loose access to the then known perks, now the bonuses I mention, when you leave the guild(You loose the rep with them upon joining a different guild). Specifically, you unlearn recipes, and guild heirlooms are returned to the guild bank.

This is from a while back, and since then I've seen them split the bonuses into two categories - player and guild bonuses. You'll also note that some of the items listed in the windows have "Guild" in the name - the pets don't, but the mounts do.

One wall of text later, we arrive at my point(I should stack haste); The "Flying Guild Mount" is obviously a guild object, not a player object, so will likely only be available while you are in the guild(and probably at exalted rank), but things like the "Snail Pet" lacks the word "guild".