No matter what exactly it is you do on your computer, there are pretty much two ways of doing it. You can either go easy on the computer, or push it for all its got, with the only exception being people who buy a maxed out Mac Pro to 'surf e-mail' and 'read the inter-web'. If you are going easy on your computer, you probably don't really care about what's going on behind the scene, however, those who push it all the way are going to want to know about processor load, memory usage, amount of space available, and so on. For that kind of thing you can either use OS X's default Activity Monitor which is designed to be more of a debugging tool than anything else, or a dedicated monitoring application that you are going to be keeping up all of the time, such as iStat.

What it does
iStat is a small program that monitors and displays information about the current state of your computer. This information ranges from the CPU load to the uptime and battery status, and is great when doing tasks that require every once of power the computer can put out.

Working with it
Like all such applications, iStat displays all the information in a floating window whose contents can be easily customized.

The main areas where iStat can provide information are: CPU, Memory, Disks, Network, Uptime, Temperatures, Fans and Battery. For each one of these areas, the information can be shown regardless of your preference, and its usefulness to you. Also, for areas where there may be several items, such as multiple hard drives, you can opt to show or hide each one individually.

Once you decide what information you want displayed you are probably going to want to change how the display looks and behaves.

Looking good
All the information iStat has is presented in a window that can function is several ways. It can either be a normal window; or it can be at the desktop level, meaning it is somewhere between the desktop background and your icons; or it can be set to stay on top of all other windows so that it will always be visible.

The way this window looks can also be customized by hiding or showing various elements, and changing the colors of the text displays. Unfortunately, there is no option to customize the colors of the graph displays, other than the four presets which do not really offer a lot of variation, some of them having very striking colors. Last but not least, the background of the window can be made transparent so that only the information itself is visible, but this also has the effect of making it rather unreadable on the wrong background.

Dead weight
One of the most important aspects of this kind of application is how compact it is. After all, you can easily see all the information regarding your machine in a fullscreen window, and then some, but that is not the kind of program you want to have up and running all the time. As such, monitoring utilities should provide as much information as possible per pixel so that it's not a waste of screen space.

Unfortunately, in this respect, iStat is a horrid flop. It takes up a lot of space, both vertically and horizontally, and there is no way to change the way it presents the blocks of information one after the other; also, there are no levels of importance to the information it shows, with everything being chucked in there.

For reference, iPulse displays all of the information that can be found in a full iStat strip except for the fans and temperature, in a block that is about 10 percent bigger than iStat's CPU block. Only the top values for each area are shown in iPulse, with all the detailed information being housed in floating windows that appear when you mouse over the respective gauge. iStat does no such thing, and takes up a lot more screen space. Keeping it up all of the time, on top of other windows, means killing quite a significant amount of your screen, and making the window transparent makes the information difficult to read.

The Good

Looks good and offers all the information that you could possibly want, easy to set up and customize.

The Bad

Very poor information per pixel ratio, with a lot of screen space being wasted to display the information that other programs can fit into something the size of a single iStat information block.

The Truth

If you are looking for an activity monitor, that you can keep at a desktop level, or as a normal window, iStat could serve you well. If you are looking for something that you can keep up 24/7 above all other windows, then you might want to consider another program that wastes less screen space.

Here are some screenshots, click to enlarge: