I've used Magento a lot since 1.3. And Magento team had improved the performances of it a lot but now it is "after 1.6" era. But the speed of Magento is still not very good.

There're a lot of post discussing how to improve it, for example:

gzip compression
minify HTML, CSS, JSS (remove all unneccessary white space)
Optimise your images
Disable any unused modules 5.Combine external CSS/JS into one file
Cachefiles that can be cached
Etc.

However, can someone shad some light on the bottle neck of the slow speed of Magento from a programming framework level? And how much can we improve for that?