Carry: Push Run

Well I usually get [*] Sage's Mask as an early item. If things don't go quite as well as I would like i sometimes upgrade it to [*] Oblivion staff for a reasonably cheap all purpose weapon. Speed, damage and mana regen. If things are going well then I don't tend to bother upgrading as I'll shoot for higher dammage weapons earlier.

Based on your build order and the fact that you do not get manta before Crit, an MKB going to help you more due to helping to cancel spells with a cast animation like primal roar. It also helps in sieging towers by negating that 25% miss chance uphill (it comes down to utility vs damage) Also since headshot is not a bash (headshot is blocked by bkb), you could add skull basher for an additional 10% chance to stun (w/ bkb) or ~6% chance to stun overall (w/ head shot) (I think 6% is low, but still).

Finally consider branches and blades of attack over a wraith band. Phase boots give you more damage and is the best boots mid game if you don't go for a shadow blade.

Manic:
I ususally play conservative with mana so I can go for High Damage items sooner, but I am interested in what you would do.

Tenshin:
Wraith Band is not necessary. I've changed it to optional. It's just for someone who thinks they will have trouble last hitting, which may depend not only on your skill but who you're laning against. If they have a higher attack than you then there is a certain window of health(their attack minus your attack) at which the creeps can be denied with nothing you can do about it except harass. You can close this window of opportunity for them by equalling or superseeding their Damage early game.
The whole point is to rush maelstrom after Shadow Blade, as it helps to get you gold way faster. But I've updated to include Yasha as a possible item after Maelstrom.

Please tell me if I am wrong in any way but it seems if you just add up the benefits of Daedalus and Desolator, then Daedalus just wins without question.

Daedalus effect: [On Average]

(Base Damage +83)*(Average effect of Critical=1.675)
Ignoring the Damage addition, Daedalus gives you 1.675 times your damage

Desolator effect:

(Base Damage + 60) * (Extra Damage Caused by lack of armor=6% of your teams Damage)
Ignoring the Damage addition, Desolator gives you is 1.06 times your teams damage

So Desolator would be better if you were only doing something like 10% of your teams damage to a particular target over a 6 second period. Otherwise Daedalus is better(unless you don't like what I did with the averaging of critical hits).

Why not get Yasha after your Shadow Blade? As someone said, sniper is very fragile, and the extra movement speed is much-needed. And Desolator is just so good for him, much better then a Daedalus, imho. I also don't quite agree with a Wraith Band start, but it is still viable, i guess. And why won't you finish your Power Treads, like, after your Shadow Blade?

Good to see Maelstrom in there. Recently while playing as Sniper I was called a noob for buying it, turned into quite an argument. Anyway Maelstrom>Mjolinor is a great buy for sniper. Personally I don't buy shadow blade either. I prefer Desolator, which for me is a core item for team fights. One question I have is what do you use for mana regen? Personally I try to use Assasinate as much as possible and need something to keep my mana pool active. You also make a good case for using shrapnel, I never upgrade it until I have to.

You're probably right about Divine, I've had a couple of lucky games I think. I've never lost it before. Better to put Manta and Butterfly before it probably.

But what would you do for survivability since he is 'so squishy', if you don't buy Shadow Blade and don't like lifesteal?

Good Point about Divine. I've used it as a very late game item for him and I've never lost it before, but it would be easy to loose.

I don't know about skull basher and headshot, I would be interested to know, but the active is still valuable.

As for shadow, the same thing could be said about any cloak. Clinks, Riki etc. But their cloaking ability doesn't become useless unless the enemy has a big lead and is not dying. Just like when you have Riki on your team, try to kill the player with Gem. If you are continuously making kills then they won't be able to afford buying Gem. As for dust, harassing is helpful, get them to use it often, hit and run, they will use up all they have. Even when you are revealed the extra movement speed is helpful to escape.
But at 12minutes Shadow is especially valuable, because everybody is weak and nobody is likely to spend 700 on Gem at that stage.
Still you could be right... maybe the 3k would be spent better on other things. I just usually play a defensive style. What do you do with someone 'so squishy' if you don't buy either shadow blade or lifesteal? I don't usually see people put Vanguard or Heart on him.

I've never got Satanic for Sniper before, but alot of people seem to do it, so I included it.

Maelstrom is great.

Seems ok but don't recommend divine rapier for sniper. He's so squishy all it takes is one gank with dust and he's dead, lost it and possibly thrown a game you were going to win. The number of games that get lost because someone gets cocky and buys a rapier is silly. Butterfly would be a much better choice.

I was also under the impression skull basher doesn't stack with headshot? So it doesn't increase the stun chance.

Shadow blade is also only worth it against bad players imo, anyone good will get dust and then it's 3k spent on 30 damage and 30 attack speed, not great.

Lifesteal is debatable also - only worth it if you plan on farming jungle from an early level. If there is a melee hero in your face you need to get out of there, not stand like a man.

I'm a big fan of maelstrom on sniper though, underrated item.