Obligatory I'm a Guerlain Girl and I really love the Original Queen Shalimar.
I'm not going to go too crazy describing L'Essence, and I'll try to be brief. L'Essence has a short poof of bergamot shining over smooth waves of vanilla, with a lot of powdery iris as it warms up, and a few drops of leather, resins, and musk, as a nod to original Shalimar. I do not detect the rose absolute note.
The vanilla is stunningly gorgeous. It just is. It wears perfectly, and I'm not even a vanilla hound. I compared L'Essence to Spiritruese Double Vanille, and honestly, I like L'Essence better. It's smooth, warm, enveloping, with little drops of iris, leather, musk ... but the Vanilla stars.
When I first got this I definitely liked it, but I was compelled to wear it more and more, and the more I wear it, the more I love it. Sometimes perfumes just wear comfortably and perfectly and this is one of them. Fantastic lasting power, but not too much to where it gets grating. The vanilla is a joy. There's enough original Shalimar with the leather, iris, and musk.
Guerlain hit a triple home run for their anniversary. I adore this, and I'll get a backup, too. If you like vanilla, if you like Guerlain, if you like Shalimar, definitely try this out, and more than once. I'm actually surprised at how much I love this.