As a long time Mac user I’m a numbers kind of guy, so I pay attention to the Mac’s system statistics. Mac users can check sys stats a number of ways, including the built-in Activity Monitor app in Applications > Utilities > Activity Monitor. It might be a bit convoluted, and it requires a few clicks, but Activity Monitor gives you plenty of information about the Mac’s CPU, Memory, Energy, Disk, and Network.
Activity Monitor is free. iStat Menus is not, but it’s far more convenient as a utility app in the Mac’s Menubar. If you’d prefer not to wade through Activity Monitor, prefer the convenience of a quick glance to monitor the Mac’s stats, and you have some money to burn, iStat Menus is the app to use.
iStat Menus give you plenty of drop down menus from the Mac’s Menubar. With a click you can see CPU, Memory, Disk usage, Network, plus temperatures, various sensors, and even a calendar (not sure why that’s there, but it’s handy).
The CPU menu displays the top five apps using the CPU. The sensors monitor surprised me a bit. Who knew there were that many sensors in a Mac notebook? iStat Menus is not a necessary utility unless you truly, madly, deeply need the stats visible and the Activity Monitor app is not your cup of tea.
Otherwise, iStat Menus is about as good as system monitoring stats can get, though having a window display system logs in real time would be a nice plus, and help to justify the price.