If price is a concern, and you don't want to spend over $200, there is another much cheaper option that has gotten good reviews, and that is the Suntour NCX, it sells for just under $100, it comes in 27.2, 31.6, and 30.9, it is heavier than the Redshift, but it's also lighter on the checkbook! The Suntour has far out performed other seatposts in that price category, some think it's either better, or as good as the more expensive ones, but weight weenies will cringe at the fact it's at least 300 grams heavier than others, except for the Cane Creek Thudbuster then it's about 50 grams heavier than the Thud.

The Thud uses elastomers to control the shock, those elastomers only will last about 5 years before they stiffen up due to age, but they're cheap to replace, plus you don't have the degree of adjustability you get with the Suntour or the Redshift. The Suntour you can adjust the stiffness with a tool, it does use a coiled spring so it won't stiffen up as it ages thus not needing replacing.

If weight is not a concern, I would get the Suntour. I had entertained that seatpost before I got the RedShift one, but the seatpost was going on a touring bike, and I was trying to keep the weight down as much as possible due to all the gear weight I would be carrying, so for me the Redshift was the better choice saving me over a half a pound of added weight to pedal around with.