@ Kapu, I think that there is no need for flash. She has insane burst and mobility. Ignite would be good to. There is no need to worry about being targeted until Shroud is down. But than again there shouldnt be much left when the shroud comes down.

Look at the items. Trin force is going to be the driving force here. You cant beat that item on Akali.

And as for the opening, I also disagree. Its effective, but I think that it should go more like this.

In the brush Akali waits for someone to pass by. As the pass her, Mark/Trin Force proc>Shadow Dance and auto attack consuming both the Trin Force proc and mark. Thats a insane amount of burst. Next you lead with the shroud and than than Shadow Dance to get Trin force proc> attack to consume Trin Force proc.

Opening with Mark is better for the burst than opening with Shadow Dance.

Ive played her extensively also, and I find thats best. Than again, I play AD.

@Kapu Flash i think isnt too important for akali. She can already shadow dance to chase or initiate, so ghost would be good for running away. Also, you should initiate a champion by using mark of the assasin, so your next attack will do extra damage.

There's a few things i think should be changed: First your summoner spells. Ghost and Exchaust is far fom the best combo for Akali. Flash & Exchaust is more efficient if you want to make surprise attacks. a scenario could be like this.
You stand in the brush and someone runs by. You shadow dance out, mark of the assassin twilight Shroud and Crescent Slash, then flash into the brush again avoiding getting torn apart, wait a few seconds and repeat. This will take out or at least scare the **** out of anyone. Mages such as Ryze, Janna, LeBlanc etc will most probaly be waiting for a respawn after this. Guys like Mordekaiser, Tryndamere, Xin Zhao, Malphite. Those will be so heavily injured that they will recall emediatly.

As for the Masteries. Instead of Alacrity, it's most efficient to have that one so that you can get Archaic Knowledge.
and the best build for akali is a 9/21/0. 3 Archmage Savvy. 1 Deadlyness. 4 in Sorcery (i think that's the name of the skill above Archaic Knowledge)1 Archaic Knowledge.[offense]
and the rest of the points in Defense to get rid of some of her Squishyness. Akali Excells at abilitys as Ap not melee attacks :)
And Glyphs... I would recommend dodge instead of Health Regain. Dodge is way more efficient against 1v1 situations

Also i would suggest that you rush a Sheen and eventually build a Lichbane from it later. At lvl 6 or so you can hit for 300+ with Mark of the assassin+Sheen procs together. And with the damage from Mark at around 1500 it is 450 damage from that.. Around HALF of a squishy's health at that level. and together with crescent Slash & shadow dance you can be a terrifying opponent. Even Mordekaiser with full shield will fear your strength.

As for boots. Mercury Threads is a better choice if the opposing team has CC. Taric, Sion, Leblanc, Anivia etc.

And yes i have played akali quite alot so i know what i'm talking about ^^.

Hope what i wrote can be to help :)