On Windows, Launchy is awesome. And I miss a comparable product on my Linux box. Katapult tries to fill this gap.
So far, the project-team has done a very nice job. Katapult looks nicer and friendlier that the usual "Run command" box (default shortcut: ALT+F2).
But there are two major drawbacks that still make me use the old-fashioned "Run Command" dialog. Firstly, it does not list alternatives. As an example, If I start typing "fi", it automatically comes up with "Wine file", and you canot select alternatives (for example "firefox" which also starts with "fi"). Launchy in comparison, opens up a drop-down box for you convenience. What is more, Launchy remembers the frequency of how often you launch a program (or so it seems). If it does not offer "Firefox" straight away the first time, it does so the second time you enter "fi".
The second drawback is that Katapult does not search for substrings. As an example: To run Firefox with Launchy, I got used to type in "ox". Katapult does not recognize this. A shame.
In comparison with the "ALT+F2" dialog. This dialog is pure and simple. It does no lookup whatsoever (at least in KDE) but it remembers stuff you typed in. And most people only use not more than 5 applications on a day-to-day basis. As a developer, for me it's actually only two (firefox + konsole). And rarely the Gimp.
So if I want to fire up firefox, I hit "Alt+F2, f, DOWN, Enter" Which is lightning fast. Or "k" or "g", for konsole and gimp respectively.
Unfortunately, you cannot do that with katapult. "f" comes up with "Wine File", "g" with "Gwenview", and "k" with "k3b", which are all things I *never* use.
Granted, you could argue that I could enter "fir" for firefox (3 chars are needed), "gi" for the gimp, and "kon" for konsole (again 3 are needed). But ultimately this defeats the purpose of Katapult which is to be a "quick application launcher". And both the fade-in/fade-out time plus the aforementioned arguments make it much slower than existing solutions. Even though it looks nicer.
But all is not lost. The biggest drawbacks are as said:
1) No alternative commands shown/selectable
2) Bad lookups ("Wine file" instead of "firefox", "kooka" insead of "konsole"...)
Solutions are simple:
1) Either display a combo box, as in Launchy, or make it possible to "TAB" through the alternatives.
2) Sort matching lookups by last executed date and pick the first.
Both are trivial tasks, and hopefully they will show up in future releases.