I agree with your general point about the value of abstractions, but jQuery is rarely the bottleneck where DOM manipulation is concerned. Most of the execution time in browser applications is spent rendering/reflowing content. It's only sane to use the DOM API once you've shown that the jQuery JavaScript execution is a significant portion of total execution time relative to reflows.
An interesting side note here is that the Rails analogy remains somewhat apt, in that much of the execution time in web applications is spent in the data store.
An interesting side note here is that the Rails analogy remains somewhat apt, in that much of the execution time in web applications is spent in the data store.