I've had it for about a month, and I really like it. The mouse has a great feel, though it's shaped for right hands only. I like the keyboard too - the keystroke feel is good, and the layout is fine. I hardly ever use the extra buttons on the keyboard, other than to pause/start iTunes. There's usually a sligh lag the first time you use such a button.
I have the (lx?)610 mouse at work, which is the PC version of the same mouse. That leads me to the one feature the 530 is missing: on the PC, if you click the scroll button and then roll it, it changes the zoom (if the app supports that). It could just be that OS X doesn't support that, or too few mac apps do, but if it's just a matter of implementing it in the driver, I wish Logitech would do that so I'd have the same mouse behavior on both computers. The PC mouse also has light-up email and IM buttons, but I don't use them, so it's no loss to me that the 530 doesn't have them.
My only other complaint is that the laser didn't get along with the finish on my desk (it's a textured clearcoat over wood) and the mouse was very skittish. I had to use a mousepad to make it work reliably. But that's more a problem with my desk than the mouse.