This has to be the first question, hasn't it?
Short: Maybe a Gnome shell like dashboard for Xfce
Longer: xfdashboard provides a GNOME shell dashboard like interface for use with Xfce desktop. It can be configured to run to any keyboard shortcut and when executed provides an overview of applications currently open enabling the user to switch between different applications. The search feature works like Xfce's app finder which makes it convenient to search for and start applications.
xfdashboard is not lightweight and as it depends on Clutter and OpenGL most performance issues will be graphics card and driver related.
On start-up xfdashboard first has to load a lot of graphical resources (icons, window contents etc.), to create textures and to 'upload' them to the graphics cards. Depending on your machine overall performance, your graphics cards and the drivers used it might be slow. Please consider to run xfdashboard in daemon mode because the start-up will only be done once. An autostart entry is available in session preferences but disabled by default. In Xfce you find this autostart entry to enable in your applications menu at Settings → Session and Startup → Application Autostart.
xfdashboard does not support hot-corners and likely never will.
But you can use other applications, e.g. brightside or xdotool. I have not used any of them.
It was reported that brightside is more complex one but running very good.
xdotool should be easier to configure and to use but it was also reported that it might be less useful if other applications like games are running fullscreen as they will be minimized and loosing focus if the pointer reaches a hot-corner and it will launch xfdashboard.
You now have a third option. With the release of xfce4-hotcorner-plugin a new Xfce panel applet exists which supports hot-corners performing different actions including starting xfdashboard.
xfdashboard only supports searching application by default and will never do more in the future. But it is planned to allow developing plug-ins which can extend xfdashboard's search capabilities - so-called search providers. So, some day, there might be a plug-in which allows you to search files and other sources (maybe zeitgeist, tracker etc.).
With the release of version 0.3.5 there was a small change in theming. If you getting a blank screen when starting xfdashboard then you are likely using a customized theme.
In this case remove or rename any customized themes in ${HOME}/.local/share/themes and ${HOME}/.themes which affect xfdashboard. Also revert the default value xfdashboard at the property theme in the channel xfdashboard in your settings. The easiest to archive this is to use xfce4-settings-editor. Select xfdashboard left in the channels list, then mark theme and click on Reset.
But you can re-use your customized theme. Therefore locate the layout file, usually xfdashboard.xml, in theme's folder and replace each occurrence of XfdashboardStage with XfdashboardStageInterface. Do the same with all your CSS file in the theme. If you are running xfdashboard in daemon mode, you have to restart it or set the /theme property to xfdashboard and then back to the old value to reapply your theme.