It's better than LCC. The overall design is much more ambitious, and it has handy features like being able to copy an app profile and a GUI of the hardware you're working with. I managed to get everything I needed mapped onto my Logitech G700s mouse, including a Shift-Right-Click using the Macro editor. It also enables some cool features on that mouse, not accessible otherwise.
But there are still problems. I wanted to buy a Logitech G710+ mechanical keyboard, which necessitated using Logitech Gaming Software (LGS) to access the extra keys. So I temporarily put Steermouse away and gave this a shot, since LGS "takes over" any Logitech hardware that it sees.
* Even though LGS installs a couple of extension .kext files, if you quit LGS, custom mouse buttons stop working. So you must have LGS running all the time. It can be hidden in your Dock after booting, but if you ever need to launch LGS to adjust something, there will be a giant "G" sitting in the Dock until you reboot again.
* LGS didn't display the G700s' left/right mouse-wheel tilt in the UI, so nothing could be assigned. There is a workaround to return all of a profile's settings to defaults--then, even though the wheel tilt areas don't light up when moused over, at least the assignments are floating in mid-air, and you can right-click on those to re-assign. This bug was discussed several months ago on the Logitech forums, and acknowledged. No fix since, however.
* No acceleration controls, just DPI and polling speed. On a hunch, I discovered that the built-in OS X preference pane Mouse > Tracking Speed may be intended to work alongside LGS. Setting that to the 2nd or 3rd notch worked.
* After boot, wake from sleep, or even coming back from a screen saver, LGS takes several seconds to "wake up" and start working. Your mouse will be glacially slow during this time, unless you used default DPI settings (not likely), and custom button assignments will not work.
* When assigning a key-press with modifier (for example: Shift-M) to a mouse button, LGS seems to put a lot of extra milliseconds in between them, leading to very strange results in some apps.
* The clincher: The "G" menu bar item finally crashed, and caused everything after it in the menu bar to stop responding. I got caught up in my work, thought it was only 9:35 pm, but it was actually near midnight. The clock display was frozen.
Logitech would be wise to take software development seriously, and stop farming it out to someone who only turns in updates when they can be bothered to, once per year. Logitech support staff seems to be at the mercy of this mystery developer, who may or may not even address the list of bugs collected by the time new Logitech hardware and a new version of OS X may be causing more. And who is doing QA on this software, if at all? It didn't take me more than one day to document everything here.
As a direct result of the above issues, I bought a Matias Tactile Pro keyboard instead of the Logitech G710+. It requires no drivers, has a full set of Apple-style keys (except F19) ready to assign to whatever, and my G700s mouse can return to Steermouse control. Everything works perfectly.