I tested the heck out of it before posting, and nothing has changed since then. Again, I'm using 10.6.8 and Safari 5.1.4. I upgraded from 5.0.x.
FireFox is a better browser, it's the best out there by a mile. The Chrome fanboys make me want to puke. Also, I think, it's important to support another option (as Chrome is just a WebKit browser, and Apple is the key force behind WebKit--so Google just takes what Apple does with WebKit and adds a dumb UI to it). Beyond that, WebKit is the browser base used by nearly every mobile platform, from Android to Windows Mobile--all essentially dependent on Apple for innovation.
The Mozilla team have blown me away, multiple times, with their work on Gecko. These guys are small fries compared to Apple and Google, but they keep surpassing everyone. Very sad, though, is the general public's lack of understanding regarding these issues, and the popularity of Chrome. FireFox had made such great inroads against IE, and then Google essentially rebranded Safari as Chrome, and promoted the heck out of it everywhere, across all their services, and people downloaded it, amazed at how much faster it was than IE.
Google is becoming the new Microsoft, though. They can't innovate, and just buy or rebrand technology (YouTube, Android, Chrome, etc), while employing monopolist practices in their core business--serving ads. The worst part is Google has become the primary gatekeeper of information, and their "filter bubbles" (see Eli Pariser's TED talk) are blocking out relevant information and just serving search results that make them the most money.
Luckily, there is a solution. A site called www.duckduckgo.com (or www.ddg.gg) now provides a fantastic search engine that does not filter your searches, or promote results based on ads, and does not sell your information from searches. Their service provides a secure, encrypted search and blows away the other engines. FireFox has their search option included by default (just click the search icon in FF, and you can set it to duckduck). Hopefully Apple will add this as an option in Safari soon.
As I wrote before, I use FireFox for any site I need cookies for, from online shopping to banking, or this site for that matter. It's the only browser I trust for that, and I have it clear all data upon closing. I use Safari for general browsing, as it's the simplest browser to open a ton of sites at once (with one click, I open all the sites in a genre I want).