In case you don't already know, some basic info on DROP LINKS, and my impression of the Tarett drop links as installed in my car. Experts please chime in and correct as necessary.

These are metal bars that connect the car's sway bars to the suspension frame. There are 2 in front (long), and 2 in the back (shorter). As showed in the picture below, after-market drop links improve on stock on three aspects:
1. The length is adjustable. Important for corner balancing, as I'll explain a bit later.
2. The bar itself is more robust.
3. The connection part is a teflon lined rod end (with what looks like a stainless steel ball joint), as opposed to the rubber bushing of stock.

Note that point number 3 is the general principle behind the improvement for a number of other after-market suspension components as well, such as rear toe link, dog bone, etc. You are replacing rubber with metallic connectors. In the process, possibly/probably trading NVH for precision and feedback. In addition, this is not a trail I am blazing here; I understand these types of drop links are routine for cars with racing, or even just sporty, aspiration.

The Bilstein PSS10 kit comes with replacement drop link for the front **ONLY**, the replacement front drop link is shorter than stock and is necessary. It looks like the stock drop link in the picture below, except that the bar is shorter, thicker, and the rubber part is blue in color. So unless you are using Tarett, your PSS10 installation will have a Bilstein front drop link, and stock OEM rear drop link.

Among after-market companies, there are variations. I've read -- no direct experience -- if not made correctly drop links could break. Among reputable companies, the most commonly used by Porsche forums' users seems to be Tarett Engineering. http://www.tarett.com/items/996-997-products/996-986-front-drop-link-set-996fdlnk-detail.htm . Another name that I've seen is http://www.theracersgroup.com/shop/trgracing.php; but I have no other info to report.

What the drop links are supposed to do:
1. Make more obvious/direct the effect of the sway bar on the suspension.
2. Make more obvious/direct the adjustments of the sway bar's settings on the suspension.
3. Allow for proper corner balance. Google and read on your own if you are interested as this is a long topic. I hope I am making some sense here as this is more easily understood if you could see for yourself how the sway bars are connected to the suspension frame. Anyway, very briefly, from my web base research : Corner balancing is done by adjust the height of the coilover at each corner, with a load resembling the driver *in the car* on the passenger seat. The goal is to achieve some similarity between total weights of LF + RR and RF + LR. The perfect goal is LF + RR = RF + LR, but most would settle for something within a few percentage points of each other. The driving goal is to have the car behave similarly between right turn and left turn.
At any rate, when corner balancing is finished, the distance between the suspension chassis and the sway bars are possibly different at all 4 corners. If this difference is small, and if you are not a perfectionist I assume, a fixed length drop links will be fine. However, if you are of type A personality (and you know who you are ), then you must have at least one front and one rear drop link to be adjustable in length, otherwise a preload will be placed on the sway, which I've been told is not a good thing.

Anyway, back to the drop links, here is my impression of the effect of the Tarett drop links, versus stock:
Without: Car is more quiet, softer, sometimes feel "bouncy" (that's the best word I could think of). With Tarett: Car is a little more noisy (road noise transmission through tires), feels stiffer for sure, but also more planted and precise.

I guess the surprise part about the drop links is that just changing the drop links make the suspension feels stiffer overall and the car feels more "planted" even in straight lines. I was expecting changes only in corners, as if you think about it, that is supposed to be the only time when sway bars' effect come into action. There is a tradeoff of stiffness versus precision and better road feel here. So I think maybe add this in the second phase, if you somehow feels car is a little "bouncy" without it.

GT's impression of the drop links as reported above, is similar to mine, except that he did not notice any additional road noise. My point about a little more road noise is perhaps mute, because after the FANTASTIC, MUST-HAVE Cargraphic Loud Exhaust is installed, I am now thinking "what additional noise?"