I know an anecdote isn't data, but here we go:
I often have >100 tabs open. I also sometimes have to restart my mac, and reopen those tabs. While Chrome then struggles for a few minutes, it doesn't take half an hour, like this article suggests, to open 100+ tabs.
And I did switch to Chrome from Firefox, as it seems to handle a lot of open tabs a lot better.
I'm pretty sure the total time depends on which webpages you open.
Also please note that this is for Firefox nightly (8) only. This might also be true for FF 6 and 7 but nothing before that. Memshrink enhancements have only started at FF 6 (which is not yet released as stable, but soon)