In addition to total time elapsed and time until next render, the status bar displays a lot of useful information.
Sampling Level: A metric of how far along your render is. Each whole number step takes more time than the last but results in equal visual improvement. In other words, it is logarithmic, not linear. For more information on this, see Progressive Rendering Basics.
DE speed: Stands for density estimation speed. This is a basic measurement of how fast your fractal is rendering. It depends both on your computer specs and your parameters. Inefficient params or params with complicated plugins often render more slowly.
- Efficiency: the nature of the IFS algorithm means that some samples fall outside the image frame and do not contribute to the image. Efficiency is a measure of what percentage of the calculations are contributing to the image. Zooming and transparent iterators both decrease efficiency. A low efficiency contributes to a low DE speed. That said, low efficiency should not be viewed as a defect; it is merely a property of your paramset! In general it's not something that can be "fixed" without radically changing the fractal or camera settings.
But When is My Render DONE?
Chaotica is a progressive renderer, meaning it will render indefinitely if you let it. You can save the render at any time, judging for yourself when the image quality is good enough for a final product. As a rule of thumb, a sampling level of 13 is usually sufficient for most fractals, though this can vary.