First, I am going to discuss the options for noise canceling headphones. Then, I am going to go into detail about the Bose QC2 headphones.
If you are looking for a great pair of high-end traditional headphones that cup your ear, you are looking in the right place; the Bose QuietComfort 2s are for you! If you are an audiophile (probably not if you are considering buying something from Bose) then look at the Sennheiser HD 650s ($400). If you don't have a large budget and want reasonable noise-canceling, then look at the Sony MDR-NC6s ($35). If you like the supra-aural style of the Sony MDR-NC6s, but want a higher quality headphone, then wait for the Bose QuietComfort 3s ($349, release date June 15, 2006). If you are looking for noise canceling while operating landscaping equipment and OK audio performance, then look at John Deere's Noise Canceling Headset ($89). If you are looking for a really lightweight supra-aural noise canceling headset, then consider the Sennheiser PXC 300 ($150). Finally, if you want noise-caneling ear canal headphones, then the Etymotic Research ER6i's ($85) are for you.
The QC2 comes in two flavors: champagne and silver (2005). The older champagne version has a problem with the headband breaking. If the headband breaks during your warranty period, Bose will send you a brand new pair of silver QC2s. The only other major difference between the two flavors is that the silver headphones work with Bose's cell-connect accessory. The cell-connect connects your compatible cellphone (there's a list on Bose.com) to the QC2s and has a mic. I personally don't know why one would need this accessory... but it's a neat add-on. I have used the cell-connect and QC2s with my Motorola E815 with no problems (other than the fact that I wasn't sure how loud to talk).
The QC2s shine when worn on airplanes, trains, and public transit. They are also very good in the office to drown out the hums of air conditioning and computers. THEY do not make it completely quiet. High-frequency sounds such as people talking are NOT canceled out.
I find the QC2s to be very comfortable. Make sure to test them out before you buy them, because the circumaural design is not for everyone. The headphones come with everything you need--1/4" and 3.5mm connectors, a great semi-hard shell case, and more. The strap for the case is not included with the silver headphones. The earcups on the headphones swivel to flatten and fit inside the case. An iPod can easily fit inside the case, and an iPod Nano can reportedly fit inside the small clear velcro case that initially holds "customer courtesy cards" (which are business cards that you can give to people that ask about your QC2s).
Make sure to stock up on AAA batteries for the QC2s. The QC3s use a custom Bose rechargable lithium battery instead. Battery life is good, and a light will blink on the side of the headphones when your battery is low.
Overall, I'm very satisfied with my QC2s, and I think other people are too. I even saw someone wearing them while driving! (Don't do that).