When Microsoft stopped supporting IE a few years back, I switched to Safari. I was getting a lot of page errors with Safari, so I switched to Firefox, and have been happy since.
I use Safari 3.1
I very occasionally use Firefox, but Safari is my main browser.
I’m currently a Demeter user. It’s a Shiira variant, and Shiira in turn is a webkit-based browser, therefore sharing many of the underpinnings of Safari.
I do not care for Safari or Firefox. Lots of little things, but high on the list for any browser I’m going to actually use is that the contextual menu has to provide the option of opening a link in a background window. Not background tab. Not new window in the foreground. Background window. It’s how I work.
Safari works fine for me most of the time, but I use Firefox for a few sites that don’t play well with Safari. I’ve also found a couple of sites that have features that only seem to work in Netscape Navigator. Seriously. Including the official Walt Disney World site.
I was dedicated to Netscape since I first came online ‘last century’. But the fact that it’s pretty much dead has led me to use Safari more. Kind of a problem, as I use Hotmail frequently. So, after reading this thread I went and downloaded Firefox, and like it very much.
Safari actually has a way to do that: Apple-option-click. 
Firefox. Safari is TEH SUXXORS.
Seriously, I used Safari on my mac for months, and just never got taken with it. And one day I had to install Firefox for a work thing, and I never went back. Firefox is just more comfy.
Safari. I just upgraded laptops a couple weeks ago (got me a shiny new MacBook) and I haven’t even bothered to install Firefox yet. I only had it on the last one so I could buy jeans from Gap’s website, and would use it if YouTube was acting like an asshole, it would often work a bit better in Firefox.
When I have to use PCs on campus I always use Firefox though.
Ooh, I hadn’t been familiar with PithHelmet, but I’ve discovered I like it. I use NukeAnything and Flashblock with Firefox, which takes care of most annoying things, and had been wondering if similar things existed for Safari.
Do you mean to view it, or to update? If the latter, do you use Blogger? I’ve found that a lot of the formatting on the update page gets a little bit crazy when you try to use Safari.
I use FF on Windows and Linux at work, but Safari is perfectly adequate on my Mac at home so I never bothered installing FF on it.
Opera
Occasionally Safari or Firefox on the rare occasions something refuses to play nice with Opera.
i use Firefox on my Mac and on my Windows laptop. I’ve been using it for years and haven’t found any reason to switch.
Safari and Firefox (and IE when I need to use the supply room database, which does not play nice with either of the others). I switch back and forth a lot because both crash and / or hang incessantly; can’t someone out there please figure this out and fix it?
JRB
re: Open link in new background window
Well, Netscape 3.0 has a way to do that, too: copy the URL from the address bar, new window, paste, hit enter, then bring original window to the foreground. While ⌘-option-click is a bit easier than that, it’s not enough so to count. It needs to be part of the contextual menu. If I have to reach for a modifier key on the keyboard, I’m not happy.
Like MrJackboots, slaphead and Basandre, I’m an Opera user. I’ve used it for a decade so there really wasn’t any other option. I’ve used it on numerous versions of Windows and on Linux, so why would I switch for the iMac? It does everything I want and more. Then again, I’m probably not a typical user: I made the switch to platform agnostic packages a while ago so I’m not locked into any specific OS.
Another predominately Firefox user here. I use Safari every once in a while, but mostly it’s Firefox.
One of my favorite features is the skins. I thoroughly enjoy changing the look of my Firefox windows based on my mood/season/holiday. Silly but true. 
You’re the anti-me.
Firefox. The extensions are great, and I like the fact that it saves bookmarks in an html file that I can easily access via http from elsewhere. In fact, I’ve been building off the same bookmarks file since 1995 or so, back when I was on Netscape under Windows. Went from Netscape to Mozilla to Firefox, never bothered with IE or Safari.
Only thing I hate about Firefox is that it leaks memory like craaaazy.
I just use Safari. It works fine for all the sites I visit.
Safari, OmniWeb, and, rarely, Opera. I’ve never cared much for Firefox, which is slow and bloated without being featureful out the box. Plugins are often buggy and tend to slow things down even more, and—on top of that—they tend tend to break whenever Firefox updates. I’ve heard that Firefox 3 will fix the speed issues for the most part, but it still doesn’t behave like a proper Mac application. Oh, it looks the part a little better, but the context menus are wrong, you can’t click and drag the unified toolbar, many of the controls look non-native and out of place.
(Apropos of nothing, Firefox 3 is probably the ugliest Windows application I’ve seen in a while. How they’re claiming this release to be an aesthetic victory is a mystery to me.)
OmniWeb is a great browser with quite a lot of features I like: decent ad blocking, picture tabs along the side, Opera-style workspace saving (i.e., it keeps histories between browsing sessions). This latter is almost a necessary feature for me. Firefox and Safari-style workspace saving suck. OmniWeb does cost money, however.
As for Opera—well, I have a soft spot for it, since it’s the only browser I feel is worth using on Windows. But Safari is recently faster and works better with some sites, and OmniWeb does everything I want from Opera.
You can still get IE for Mac, if you look around; I have it installed on this Leopard machine as a curiosity. But there are more serious contenders to try—Shiira was mentioned; though its most recent release is egregiously broken, it has a few neat features for the hardy. iCab just had a new release, shedding its homebuilt rendering engine for Webkit (good luck finding a Mac-only browser that doesn’t use WebKit, besides Camino).
Edit: fixed flow.