The big picture
These tests were conducted on a Windows 7 x64 laptop running a Core i7 Q720 CPU with 4GB of DDR3 RAM. For each browser tested, we closed and relaunched the browser before each trial, and the window size was consistent across all trials. The document for the benchmark was very similar to our standard business process template, of moderate complexity. We ran four trials for each browser, and the results shown here are averaged across those trials.
Some final notes on Firefox 4 Beta 6
In several trials on Firefox 4 Beta 6, performance absolutely tanked due to the browser doing some unknown background work. These trials were discarded for the purpose of this data, but it should be noted that Firefox 4 may have inconsistent performance for certain types of modern web applications, like Lucidchart.
Some final notes on IE9 Beta 1
Run the benchmark yourself
This benchmark can be run by anyone in Lucidchart. First, sign up for a free account here. Then create a document that you'd like to benchmark. Right-click the block you'd like to have dragged around the page by the benchmark, and click "Bring to Front." The benchmark uses the topmost block for its test. Then click the tools menu, and select "Benchmark Performance."