I never know if Address Book is called "Address Book" or "Contacts" or whatever. On iPhone it's called "Contacts" and on OS X it's called "Address Book", causing all the confusion. I rarely use it so it's not on my dock, but when I use Spotlight to open it, I sometimes sit there thinking what the hell I'm doing wrong as it's not showing up.
Same thing with "System Profiler" and "Activity Monitor". I'm sure that when I want the Activity Monitor, I start typing "System..." and I don't get the right app. If I had icons of both of them next to each other, it would take me 0 seconds to figure it out.
I don't think of Spotlight as an official solution to launching apps. It's handy when you quickly need an app that's not on your dock, but there has to be an icon view for all your apps, in my opinion. This is the 21st century, we no longer use command lines to do things and the GUI has become the only way to do things. It's nice to have some command-line style things such as Spotlight to make things faster, but there simply has to be a graphical way to do things too.
Opening Finder and clicking Applications and then scrolling through all the random folders that installers create is a pain. Then you don't know if what you're looking for is supposed to be there or in a folder. The launchpad solves that issue as you can rearrange everything the way you want, and even remove unwanted shortcuts.
Using a stack to do this is not an official solution. I find stacks buggy, scrolling is laggy and there's no way to rearrange your icons any way you want. In stacks, you also have to either use the entire Applications folder, which is annoying as there are many things in there you don't want, or you have to make a special "Alias" folder where you put the aliases to the apps you want. That's hardly official and elegant, it's more like a workaround than the way Apple meant things to be.
Launchpad is the way Apple meant things to be. I think it's good, but maybe it should not take up all your screen.