I'm on SL 10.6.1 on a new 24" iMac bought just weeks ago. I have no issues with this machine nor with any of my installed software.
Was very much looking forward to this update for SL, slow as it was in coming, because it addresses an important part of the experience of using my mac.

This version of LCC is probably one of the worst updates in the history of updates!
It is buggy, outlandish nonsense.
I am familiar with previous versions of this software for my MX1000 Laser Mouse, which have worked as expected.
For this version, I set up the buttons as usual, so far so good.
But in use, was beset by bizarre problems. Where do I begin?

I had to uninstall LCC just to be able to write this review! Now things are back to normal.

• Contextual menus don't work: if they come up the options don't respond to mouse movement, ie right arrows don't respond, no menu items get highlighted on mouse moving over them. And if they do respond they quickly disappear before you get a chance to click on one.

• In the Finder, just passing the mouse within a window makes it scroll horizontally & uncontrollably back & forth.

• Perhaps most bizarrely, just mousing over my dock - without clicking - jiggles the icons about and fires up random programs!

• Bizarre - in Entourage, just mousing around within its window rearranged the view so i lost columns etc & by just moving the mouse, it had managed to open several windows of messages, & i kept getting dialogue boxes asking me if i wanted to delete messages - all this happened in quick frightening succession.

After uninstalling LCC I had to spend a bit of time re-arranging Entourage the way I like it again - luckily no messages were actually trashed. It was as if the mouse had a life of its own without intervention from me - except just to start a movement & then it would wreak havoc on whatever the cursor happened to go near. It was like a crazy episode of the "Lucy Show" on steroids!

• Using the application switcher doesn't allow you then to select the application you want because the switcher itself disappears as soon as you use the mouse.

Logitech - do something about it! You knew Snow Leopard was coming - this is inexcusable! I'm happy with the mouse itself - just the software stinks.

And to add the final insult to injury, when you try to access Logitech's email support pages, they are conveniently unable to respond to because they are overhauling their support pages until Sept 28th!

DON'T release a major update when support is unavailable!! This shows an amazingly cavalier attitude towards your (Mac) customers.
I'm just glad Logitech doesn't design cars. They would have had a class action against them by now....