The dev preview of win 8 has been out for months, and the RTM/Consumer preview will be out on the 29th.
RTM means ready to manufacture, the version coming out on the 29th will be very similar to the end retail product.
Dev preview was freely downloadable, so will the RTM/consumer preview version.
RTM means release to manufacture.
After the consumer preview there will be a release candidate and then release to manufacture. There is no current ship date for RTM but it's widely believe to be in 6 months.
Any minor annoyances could easily be changed in that time. Now is your chance to find them, when it's free to try & you might stand a chance of getting them changed.
Major changes would be harder to predict, although it's known that Windows Media Centre doesn't come in the consumer preview.