They've been my favourite band for the last five years. Basically their arguably the biggest Prog band around today, and definitely the measuring stick for all other Prog Metal bands.
They've been around over 20 years and have accomplished so much. With 9 studio albums, 5 live albums, loads of "Official Bootlegs" and DVDs there is a lot to choose from when it comes to Dream Theater.
Each member is technically sound on their respective instrument and all have a huge reputation in that area ie. Bass player John Myung is well known/respected amoung bass players, and many consider him one of the best players today.
Their music is a mixture of many things. Mainly heavy, technical and epic metal. But sometimes with other influences from genres like Jazz, Classical and Funk. Complex song strutures and long instrumental sections make this a demanding band at first listen, but once you know the songs better you'll be glad you stuck with them. They are also known for the long songs and "Easter Eggs" in their albums/songs etc... finding ways to link a lot of them together.
Over the years they have established themselves in a huge way. With contacts all over the music spectrum. They signed with Roadrunner Records last year to release their first truly "mainstream" album, but this band is no way an underground act.
Each member also has countless side projects/guest appearances etc. So many that it's hard to keep up with 'em all. Some of these are also considered "big name super groups" that produce technical music of the highest order. These include "Liquid Tension Experiment", "Transatlantic" and "Mullmuzzler".
While some people will complain that it's all "mindless shredding" and "Soloing for the sake of it", others prefer the crazy time changes and incredible chemistry this band has. I personally feel that this is without a doubt the tightest band in the world. Any of their lives DVD's will prove that. Guitarist John Petrucci and Keyboard Player Jordan Rudess are both absolute virtuosos who feed off each other very well. Bassist John Myung is amazing to watch and Drummer Mike Portnoy is forever involved in "Best Drummer" debates.
However, it all comes down to taste, so I can only link you to these two sites and you can draw your own conclusions. If you need any recommendations, go with either "Images and Words", "Scenes From A Memory" (Which may be a bit too ambitious for a newcomer), or "Train of Thought" for a more metal feel.
http://www.progarchives.com/artist.asp?id=378
http://profile.myspace.com/index.cfm...7-6dbf19aae325