Try removing with() from offset.

[flesler]

Maybe, removing the with() call from offset() can improve its perfomance. The saving in bytes is really small, so if it does hit on perfomance, then it might be better to remove it.

[flesler]

with() removed, jQuery browser is cached into a variable

[flesler]

Replacing css for curCSS inside offset, caching getComputedStyle

[flesler]

I made some real tests, the with() didn't seem to matter much. I tried replacing jQuery.css for jQuery.curCSS because that was a useless call. The time got lower and saved many calls. Then cached document.defaultView && document.defaultView.getComputedStyle in a var, and that reduced the time. I tried all this many many times back and forth to discard CPU interferences. The element that I called offset on, had 7 parents, and then the body. The latter was its third offsetParent.

Regular

Profile (21359.375ms, 186011 calls)
offset(500 times) - attempt 1: 5359ms test.js (line 17)
offset(500 times) - attempt 2: 5406ms test.js (line 17)
offset(500 times) - attempt 3: 5359ms test.js (line 17)
offset(500 times) - attempt 4: 5297ms

curCSS 4 css 

Profile (20296.875ms, 148011 calls)
offset(500 times) - attempt 1: 5093ms test.js (line 17)
offset(500 times) - attempt 2: 5000ms test.js (line 17)
offset(500 times) - attempt 3: 5109ms test.js (line 17)
offset(500 times) - attempt 4: 5109ms

curCSS 4 css, defaultView cached

Profile (16203.125ms, 148011 calls)
offset(500 times) - attempt 1: 3984ms test.js (line 17)
offset(500 times) - attempt 2: 3969ms test.js (line 17)
offset(500 times) - attempt 3: 4078ms test.js (line 17)
offset(500 times) - attempt 4: 4203ms

[flesler]

File to run the tests

[brandon]

Patch applied in [5274] and [5275].

[flesler]

Added some modifications to this at [5609].