KERNELG  Sorry, no. GlimmerBlocker was the first alternative that I tried. It causes Safari to stall out at random times, and created massive lag in network applications besides Safari because it's a proxy at the OS level. It is not a viable solution at all.  
(Version 12.0.2)

KERNELG  Just popped up on the radar: Safari AdBlocker 1.1.1. It's free, 64-bit ready, and the new version works perfectly in Snow Leopard via SIMBL. The installer even includes SIMBL, whereas Saft didn't even provide a link to the SIMBL web site.  
(Version 12.0.1)

KERNELG  I have used and recommended Saft for years. While hesitant, I sprung for the upgrade to the Snow Leopard version when it was finally out of beta. This was a mistake.

With Glims now available for free, the only reason I wanted to get Saft back on my system was ad blocking. I am tired of seeing the same damned "I got ripped in 4 weeks" and countless Internet dating ads. I also had many years of carefully selected ad blocking patterns built up. Why am I so disappointed?

Saft ad blocking no longer works properly.

Oh, it works if you try to load a single image directly. You'll get a Safari dialog which describes how the image could not be loaded because Saft blocked the URL based on a given pattern. But there the ad sits in the middle of a web page, displayed as normal. This occurs through refresh, re-launch, cache reset, Saft settings wipe, and even a full Safari reset. As a Saft user for years, I know how it's supposed to work and it does not. For the record, this is with the SIMBL plug-in install, running Safari in 64 bit mode. (The other methods cripple Safari, and are not an option.)

Why not just report this to the developer? Because I have reported issues and asked questions in the past and I've learned that you may, or may not, get a reply weeks later, and it will rarely be more than one sentence which may, or may not, be relevant to the topic. In other words, the message is now "go away." Message received.

I would no longer recommend paying for Saft. Good luck navigating his web site if you wanted to. If you don't need ad blocking, definitely go with Glims for free.  
(Version 12.0.1)

KERNELG  I had been using USB Overdrive with my Logitech MX1000 for years. My various experiences with LCC were very bad: It didn't recognize all the buttons on the mouse, it relied on haxies, it was not updated for serious bugs for long periods of time. But with the recent update for Snow Leopard, USB Overdrive (and Steermouse) does not support all of the buttons on several Logitech models. A fix is promised to come soon, and while I love USB Overdrive, promised features can take years to materialize, if they ever do. Some people are also saying that setup is even more convoluted than before (try adjusting tracking speed on 20 app profiles with 2 pop-up menus each). So in the mean time, I decided to give the free LCC 3.1 a try. I took some screenshots and notes of my USB Overdrive settings then used it's own uninstaller to remove it completely.

The LCC install went smoothly and after a restart, it recognized my MX1000 with no problems. I immediately notice that tracking is a little smoother. I also notice that vertical scrolling is extremely slow and/or high resolution. Better yet, tracking speed is a universal setting and not per-application. Scrolling, however, is per-app and even on the fastest setting is still slow for some. Tweetie, for example, scrolls slower on the full setting than USB Overdrive ever did. But I'm already getting used to this.

LCC's only other drawback is that there is no application profile overlap or punch through. I cannot, for example, make a profile for iTunes and reassign only the mouse thumb buttons perform keystrokes Command-[ and Command-] for back and forward, but use my global settings for everything else. In fact, I can't find a way to even copy my global settings into a new profile to at least have a common starting point. I tried using the "nothing" assignment in the pop-up menus for other buttons, but that just made them do, indeed, nothing. I'd love to know if I'm just missing the obvious here.

On the positive side, LCC 3.1 has fixed a few problems I was having with USB Overdrive and had mistakenly attributed to the mouse. The "back" thumb button was frequently registering two clicks when I'd hit it once. Tracking was very jerky in World of Warcraft when moving the camera quickly. Horizontal scrolling was more of a horizontal 10-pixel nudge, with no auto-repeat or acceleration. I couldn't assign anything to keys F16 through F19 because these were apparently new science. All of this is now history with LCC, and I'm loving that my aging MX1000, for which there is no modern equal, may still have a couple of years left in it.

I see that all is not well in comments here, and on Logitech's own forum. As I said above, I made sure to fully uninstall USB Overdrive before installing LCC, and I don't think I had any previous LCC preferences on this machine for the new version to pick up. I'm running a Mac Pro 3,1 (Early 2008) 8-core with OS X 10.6.1. There are no other input drivers running. LCC 3.1 is rocking here. For free!  
(Version 3.1)