Moreover, this post is complementary for few slides I have introduced at front-trends, specially regarding the "avoid classic OOP emulation when not necessary" point.
Even if many developers don't care, I keep saying that every millisecond gained in this first layer, the page itself, is important.
Anyway, common sense first and fast production quality, should always be kept in mind when we decide an approach, rather than another one. So, here frameworks play usually quite good role, the one to bring same functionality cross browser.
But what is a browser?
Layer #2: The BrowserAs libraries are considered an abstract way to reach same goal in all browsers, browsers are simply abstract applications able to bring the web cross platform.
Layer #3: The Operating SystemWe are even lucky if the browser deals directly with the operating system graphic API, since many other middle layers could be part of this stack ( flash or third parts plugins, as example ).
You cannot expect that Linux, Mac, and Windows, just mentioning fews Desktop related ( more choices on mobile world ) magically display and provide browser functionalities via the same API. We would need something like a jOSQuery library here to make it happens ... but even worse, every operating system may have another abstract layer able to use, as example, Hardware Acceleration.
Layer #4: The HardwareOpen GL ES 2.0 is simply another abstraction able to transform API calls into specific hardware driver calls which means that starting back from the DOM and the used WebGL or CSS3 with HW support, things have been modified, translated, re-created at least a couple of times.
In few words, if we asked too many things to do on first abstract layer, and being the first the slower one, nothing can be that fast.
As SummaryWe, as web or scripting programming languages developers, rarely think that performances on the highest level ever can be that important but unfortunately, that highest level is the slowest one ever so, specially if we would like to reach best frame rate via canvas, WebGL, or CSS3 animations, it's highly recommended to be sure that the strategy/code we are using is the best one for our requirements.
As example, if we spend just a millisecond more to create each object we need for a single frame, we can easily switch from 30fps, a decent visual framerate, to 29 or less, were things will start to be visually slower for our eyes ...
Finally, kudos for Opera Mini and its growing market share, I am pretty sure it will become soon the IE for mobile platforms, making developers life easier, being a portable browser fallback for whatever website or application, hoping will not have all IE problems we all know.