I need a new stem because the one that came with my bike is too long. It is carbon, replacing it with another carbon stem will be far more expensive than buying an aluminum stem.

Does the carbon stem offer advantages that substantiate the extra cost?

Looks and a few less grams; that's all.

Have you talked to your LBS. Most shops will swap out your stem for free or for a nominal charge if you haven't own the bike very long and haven't damaged it. By this, I mean a few weeks to a month.
In answer to your question, I don't think a carbon stem is worth the money, except to impress your friends.

Advantages: They look freaking awesome.

Disadvantages: They don't look as awesome when you get a big ass crack in it from the bike falling off your roof rack.

Carbon shatters, aluminum dents.

That's why I will never ride anything other than an aluminum bar and stem, even though they may not be in keeping with my Weight Weenie tendencies.

Get aluminum

Aluminum us usually lighter and cheaper. and IMHO they look better than "The Plastic" stems.

+1... got it from PBK and love it!

Yes.

Aluminum is the choice to make.

As recursive likes to point out...aluminum can crack as well....but for bars and stems it is my choice.

I'm a fan of carbon bars for the vibration dampening, but I still run an aluminum stem. My LBS talked me out of getting a carbon stem - they said the dampening would be minor.

Who makes that?

Deda maybe?

+1. I'm a weight weenie, but ride aluminum stem/bars.

Ritchey WCS 4Axis, they are on sale at Performance for $79. They weigh less than most carbon stems and are stronger. If you are looking to save weight, don't waste your money on light weight parts like stems. Put your weight saving dollars into the big things like wheels and cranks and get a substantial return on your investment.

Alpha Q Prolite stem is stiff, light and cheaper than carbon.

don't waste your time with anything else.

Doesn't really make sense not to. The weight difference as far as I remember is TINY. Same with carbon seatposts, carbon cranks (haven't looked at these in a year or two but as far as I remember), hollow pin chains, etc. The difference is pretty small.

+1 I love thomson products. They are a huge CNC company that made a few bike parts on the side. Top notch stuff.

I too am a fan of Thomson stems and seatpost. I'm very picky about stems because I notice when the flex of a super light stem. there are lightweight stems out there, but depending on the length, you might notice them flexing when you stand on them. Thomson is one of those that just won't flex. I have the older elite model and I like the design where there are no screws at the back of the stem...my knews brush on the swrews if I'm not careful when standing. I agree that carbon bars help with road vib, but there is not much weight savings and there is the danger of the bike falling and cracking the bar. if your LBS will let you try some stems before purchase, all the better.

carbon bars and road vibration is almost silly. Tires will do more for you in that department. Carbon and handlebars come into play when the design of the bars is to dramatic to be made from metals. Carbon allows for more ergonomic shapes etc.. as for weight and road dampening the design will help with that more than the material.

I actually could feel the difference between the aluminum and carbon FSA bars. I ended up with the carbon bars, and I'm happy about it.

Still ride a $30 aluminum Reynolds stem, tho.

oh, right - that's why there's no difference in ride between a steel, an aluminum, and a carbon frame.

+1 Have this one myself, quality stem! and rock solid!

Get an aluminum stem. Once you are happy, sell that carbon one on ebay. Now you've made enough money to pay for the al stem plus another incase you decide to change lengths again.