The two best things that I have done for my by were getting a proper sizing session and adding a dropper post.  Realistically, just about any dropper post can increase your riding skills by giving you more room behind the saddle for getting around technical downhill obstacles.

Product: KS-i950r dropper seatpost

Manufacturer: Kind Shock

Rating (1-10): 6.5 of 10

Pros: Unlimited drop range, solid button

Cons: Durability, serviceability

Configuration: 30.9mm dropper seatpost with no setback

Verdict: There is no finer seatpost

Website:  http://www.kindshock.com.cn/en/product.asp?fid=7

Review: This purchase came about because after being sized for my bike, the seat was a lot higher than I was comfortable with.  It was great for climbing, but when it came to descending, it was a lot harder, so, enter the dropper post.

The KS-i950r is now being replaced by the Lev, which is in my opinion a better design because the cable connects at the bottom, not under the saddle. 

The post itself is great because it has an unlimited drop range.  Some of the posts on the market have 2-4 stop positions, but this one will allow you to drop an unlimited range (up to the end of the post) so if you need to drop it a bit but still want the stability of having a seat below you, you're covered.

The seat post has a collar that unscrews, allowing you to add some grease (I recommend Phil's) under the collar to help keep it running smooth.  This is an important feature because over time you'll find that dropper posts do not have the same durability as forks.

One nice feature is the push button which has a very solid feel and a low profile design.  Some of the droppers on the market have "levers" which stick out and are prone to breakage.  I was able to flip my bike onto the trial more than once to do a drive train repair without worrying about the lever.  It fits easily between the grip and the brake lever on the bar, conveniently locating it for easy access.  I highly recommend putting it on the left side.  I have seen a few people mounting on the right but if you think about the typical usage, all of your hand action is happening on the right, so the left hand is generally free.

Now for the bad news.  About 13-14 months into the use it started sticking.  The last 3/4" did not extend so often I found myself having to grab the seat with my legs and pull it the rest of the way up. A couple of visits to the shop (for other things) meant some mechanics had their shot at it.  It would always work great for about 15 minutes, then slip back into the same problem.  Finally, about 2 miles into a city park lap it finally gave out.  Would stay extended no matter what I did.  It was like riding a dirt jump bike back to the parking lot.  I sent the post back to KS and it was repaired and returned in about 2-3 weeks.  

When considering my next dropper, I would probably consider KS again, but I am more interested in the durability so companies like Thomson have my attention for future products.  But, as for this shock, it was a great value for the money and a great addition to the bike.