Once upon a time one of the cheapest ways to make a tangible improvement to your enjoyment of a gadget was to invest in a new set of headphones and bin the schlocky $1 set that the manufacturer bundled with it. Now with the current fashion for noise-cancelling technology that's not so true any more; yes, there are some damned good sets out there, but they're not so cheap any more. TabletPCReview spent $110 on Sennheiser's PXC-300 from Amazon and put them through their proverbial paces.
It's an interesting review because, rather than many others I've seen, it doesn't over-egg the pudding. Noise-cancelling headphones, as any sound engineer will tell you, can't work miracles; if you're sat near the wing on your next flight then they'll do a decent job of masking the engine noise, but if you're more keen to block out the random shouts of passing sea-lions then think again.
The Sennheiser's magic comes from that unwieldy 5-inch long tube, containing all the NoiseGuard circuitry and enough battery life for 50 hours or so (short of the 80 hours the company boasts). Tests with different types of music round out what is a very thorough review, and well worth reading if you've been thinking of binning your current cans and upgrading to something a bit more special.
Sennheiser PXC-300 Noise Cancelling Headphones Review [TabletPCReview]