Part of the health care reform bill is a new 3.8% tax on the net investment income of taxpayers with AGI of $200k single/$250k MFJ. Net investment income includes interest, dividends, capital gains net of losses (not adjusted for investment expenses), net rental income, and net passive business income. This tax will be collected via the tax return but must be considered when determining withholdings and estimates as of 2014 to avoid penalties.
With higher capital gains rates already expected effective 2013 plus this tax, 2012 seems to be the best year to sell capital assets with a gain if at all possible. Some people may want to sell and repurchase the same assets just to recognize the gain at the lower rate. Losses will be more valuable to offset gains in future years.
It may be best to sell sooner rather than later as many could rush to sell assets later in the year bringing values down.