Adobe released the full version of Lightroom 5 today after a two-month free beta program. It'll be $79 to upgrade from earlier versions and $149 to buy new.
At $79 I'll be upgrading, even though the improvements from version 4 to 5 aren't nearly as compelling as the jump from 3 to 4. I expect the automatic straightening feature to be a time-saver -- it corrects for wide-angle distortions of buildings, not simply things like crooked horizons; and a beefed-up healing brush that lets you work on more than just circular-shaped sections of your image. Finally, I'd like to encourage Adobe to keep Lightroom as a stand-alone desktop license option and not force us all to subscribe to Creative Cloud.
Should you upgrade? If you're a heavy user who does an increasing amount of serious photo editing in Lightroom, you may want to consider LR5, since some of the new tools will save likely save time and reduce the number of photos that need fixing in full Photoshop. If you primarily use Lightroom for workflow and basic edits such as cropping and fixing exposure, though, you'll have to decide if the new features and fixes are worth $79 or you'd rather wait until the next version.
I had a short review of the Lightroom 5 beta in April, if you're interested in more details.