are there more benefits going aluminum as opposed to carbon fiber?

I think just price.....I was looking at cf shafts for my wrx....they were ~25% lighter smaller od and twice the price of aluminum. ( aluminum has to be thicker to equal the strength of cf)

CF will also twist more before it breaks, acting a little like a sprung hub clutch. This can be an advantage as it's more forgiving.

@slates74 what was the highest speed you have gone with the new drive shaft?
The only thing that is holding me now is that I hear that Aluminum drive shaft vibrates at high speed while Carbon Fiber don't.

I like the idea of a single piece aluminum driveshaft, but I keep on coming back to the same question:

On a car that is supposed to be light and inexpensive, why did the factory choose a heavier & more expensive to produce driveshaft?

There has to be a reason they went with a two-piece shaft; such as a destructive harmonic vibration that was damaging the transmission or differential...or some other reason. Twelve pounds is a lot of weight savings in the drive train, but I'm just not sure I want to jump on this band wagon until there is long-term experience with the lightweight shafts.

so it sounds like theres some noticeable noise i remember my 1 piece ds on my 240sx made huge wining noises over time. good price though...

The gears certainly will help. I have a 4.67 in mine and gained a noticeable improvement in power delivery. Lightweight drivetrain parts could hurt your 1/4-mile since revs drop off between shifts, unlike heavier parts that carry inertia. If 0-60 or 1/4-mile is important than you'd want a solid driveshaft more for power delivery than anything.

It's to combat NVH. The same goes for the dual-mass flywheel. Lightweight and/or solid bits cause shakes, rattles, and noise that people would otherwise equate to an issue.

i wont be there this week cause im in VA but next week if the weather is good ill go. police dam near host the meet lol so zip tie a front plate lol

I've had the car near 100 mph so far and haven't noticed any vibration whatsoever. In regards to any extra noise, as I said before I can't discern any difference at this point at all. The only difference I could at first was that I could hear the typical rattle sound that the transmission makes at under 10 mph slightly more clear but even that has been hard to remember the difference of after driving this much. I really can't say enough good about this mod for the price point. The car feels tighter and more responsive overall with no notable downsides.

@slates74, i need to get a ride along one time in the car and see how the car feels with the new driveshaft. I'm debating on getting this...

I like the idea of having a lightweight drive shaft.. But why did the OEM choose to use a 2 piece system? Clearances perhaps? Cost? Maybe a stock part from something else? Would like to know some of the reasons behind the OEM design and choice.

Update from Mark, the yokes are machined from forged pieces and this particular driveshaft is rated up to 700hp.

The two piece construction is supposed to dampen sound more than a one piece but speaking from experience it's not an issue at all. In terms of clearance, after I took the car out for a drive yesterday we jacked it back up and inspected for any points that may have come in contact with the driveshaft and as expected there were none.

I would think its more adventageous for clearances since its angled. The OEM has to consider all scenarios the DS might encounter under extremes. As the DS will flex and move as the suspension and rear end move about. Nice to lose that weight on a reciprocating piece.. Enjoy..