I've been playing this build for a few days and it's doubled my kills and cut in half my deaths. Most of the time i use teleport and either flash or ghost for my tops, but i've found that building mass sustain early with health reg quints, doran's shield and the new item face of the mountain rushed, combined with the amazing escape and chase capabilities of a combined flash and ghost, make nasus (almost) ungankable as well as a killing machine into late game. Try it, and you may find that like me your kills will double, your deaths will dwindle, and you'll start hearing "Nasus, too fed!" alot. I don't have time to build a super guide, but will add stuff when i can.

Nasus is the only AD champion that gains attack damage from killing minions, tower, small monsters, teemos shrooms(any thing you can destroy, pretty much (3 ad) and large minions, large monsters, and champion kills (6 ad). If Nasus were a normal adc he would quickly snowball--but his only ad damage comes from siphon strike his Q. He is a dog with a stick, albeit a potentially big stick. Each minion killed with siphon strike is worth about 35 extra gold worth of attack damage PLUS the normal gold you get from last-hitting. This means one point of ad is only worth 11 gold to Nasus, whereas with an adc like Varuseach point of ad is worth 45 gold. In a nutshell this means when Varus buys a B. F. Sword, he drives off with an Alpha Romeo...when Nasus buys a B. F. Sword, he drives off the lot and doesn't have a Mustang, or even a Pinto,-- he's got like a shetland pony--the 1600 he spent on that sword only gives him 400 gold worth of damage. So when you understand that any item you buy with ad, or using ad runes, you will get 1/4 of the value of those items compared to other adc champions, you realize how important last-hitting is, and that trinity proc, armor penetration, attack speed, and even critical strike items, have more value to nasus than high ad items(more importantly though, are tank items that contain cdr).

If you're using life steal quints you're building into a number of weaknesses. !). You're building into a nerf, and 2). you're building into Nasus weak early game. Quintessence of Life Steal, sure, they scale best, but they don't start kicking in until around level 7. If you're up against someone who knows what they're doing you will probably loose early. Some will say that this build is good for beginners, but that's not true, in fact the opposite is true--variations of this build are better against better players and counters to Nasus. I have no doubt about this: building mass sustain, especially with the new defensive tree, allows nasus to stay in lane and farm during the crucial early game (experience, farm) longer than life steal quints. Period.
This build is (I believe) one of the best hyper-carry builds for Nasus top. It is not the best all-around build, however, because without Teleport your ability to control the map (pushing, split-pushing etc. is severely limited. Because it severely limits spamming your spells you have to really manage your mana usage into mid game, and you will find it hard to push when you really need to push unless you get your mana items early.
No, this build is good for just one thing--farming like a maniac and driving your top opponent mad

face of the mountain
This item is not core at all. It makes more sense if you play Nasus bot as a support because it allows you to farm your q and give your adc more gold and health, as well as giving him a damaging shield into mid game--i love this item. You can throw it on yourself if you're low health and the ratio comes out in your favor as far as health/damage received/dealt. If you use this item top it can be like a carrot for your jungle to come up and gank for the extra gold/health it gives, and it helps clear minion waves when another champion is near and stealing all your beautiful farm! Get creative with this item. When I play Nasus top i either get this or
Spirit of the Ancient Golem
as a counter to more difficult top opponents (this is probably still the best all-around gold item for Nasus because it gives you a mana reg boost allowing you to push with Spirit Fire and not worry so much about conserving mana). It's passive also allows you to kill monsters faster making you're ability to kill dragon and baron nashor faster with your ultimate, and maybe most important of all it gives you health combined with your early core items, plus 10% CDR--This item is core for jungling...
Athene's Unholy Grail
Rushing this item may be the only way to salvage your lane against direct counters to Nasus top like Teemo, Elise or Olaf. Rushing a Chalice of Harmony and putting 3 levels on your Spirit Fire will allow you to spam your abilities and get enough gold to buy the items you need to stay alive and farm your Q later, and if you know what you're doing you can zone out the best players with Spirit Fire and still get nominal q farm. Also Athene's Unholy Grail plus Iceborn Gauntlet geve you 90 ap, which will burn through minions and make you a pushing machine (a little ap goes a long way on Nasus).