Being interested how JPEG mini performs and works, I ran some super-scientific experiments with the Lena image. JPEG mini claim to reduce the size of compressed photos by up to 5x while maintaining the perceptual image quality.
I used IJG's cjpeg program for baseline compression (denoted JPEG) with a given JPEG quality. opt. JPEG refers to the optimized Huffman table option of the cjpeg program, smooth JPEG makes use of the smoothing (factor 30) and optimization of cjpeg.
On to the results: JPEG mini succeeds to reduce the JPEG file size, especially for very high quality factors. The perceptual quality is harder to judge, a significant drop in PSNR can be measured. The scientific aspect is the usage of the Lena image obviously. :-)