Has anyone dynomated their XD? Is it really worth it?
How easy is it and how much did it cost you?

there are a lot of threads on this, i would suggest doing a search. overall it is worth it if 1) you want to decrease the road noise level in your car, and 2) you plan on installing a high end audio system. you can do as little or as much as you want (e.g., doors only, trunk only, doors/trunk/floor, etc...). dynamat extreme is expensive, and there are cheaper alternatives that work nearly as well or as well. it also involves ripping apart most of your interior to do completely. on the other hand, it can be done little by little as you do other mods on your car. i have applied 60 sq. feet of a generic dynamat type material on all four doors and the entire hatch area. in the future i will add another 20-30 sq. ft to the floors and possibly the hood.

I will tell you that in my opinion, it is not worth it unless you enjoy working on your car and are prepared to go all the way. It takes a lot of work and you will notice an improvement, but it's really a pain to sound deaden these cars. Even after you finish Dynamatting, you're still going to have rattles here and there which develop over time. Then you have to try and fix those one at a time and they never seem to want to stay quiet... sheesh.

I did start a little DIY on this if you want to see it:
http://www.gldomain.com/elantra/BrownBread/

I have finished the project actually, or at least I've done as much as I want to -- just the front doors and the rear deck. I guess I should update the DIY at some point.

I used Brown Bread which is similar to Dynamat, just cheaper.

if you own a hatch, then the biggest single improvement the dynamat can make is in the hatch area. just applying 10-15 sq ft around the hatch floor and spare tire well made a very noticeable difference in the amount of road noise generated through that area, and there is practically no work involved, nothing to dismantle. the sedans don't transmit as much road noise from the trunk through the car as the 5-doors, so there's less of a benefit there if you have a sedan.

but i agree with swortham in that it's a huge undertaking to do other areas like the doors, floors, etc... i also think the benefit won't be nearly as great as the benefit you get from doing the trunk area. frankly i didn't notice a big difference after doing the doors. but the bass is noticeable tighter from my front mid bass drivers and less boomy.

as for brands, fatmat is the best price per square foot, if you're willing to buy 100sq. ft. just search for it on ebay. the stuff i used (dayton audio) is not as good as the fatmat and it cost me more... :(

I also used brown bread and yes, it is worth it.
I did only front door and rear and trunk 3 layer. It was not fun to install at all.

i cut up my hands pretty bad doing my trunk...i used cascade audio stuff...works really well...but there are still rattles...but not nearly as many...plus it upped my db's there is a noticable difference in sound quality and loudness