Some suggestions :
When i press the button "Call ordinary phones" I expected to get a tab with the usual digits buttons, instead of that I have a dialog box telling me that i can call phones by entering the number in the box above the contact list. Right now, i don't really see the point of this button except letting me think that I would have a phone interface when pressing it.
When i call a normal phone i'd like to get this screen with the numpad, for example when you call a hotline you often have to enter more numbers, press # or * while the call is in progress, and i think it's better to get them on the screen rather typing on the keyboard (although i think both key typing and screen clicking should be available)
When I click on a contact, it expands and some more info/options are available, to fold this, i can click under my contact list in the blank area, but if I have too much contact I won't have any possibility to fold the contact... Maybe a little button on the right of the contact to fold it should be useful.
I noticed that when i click on "Call ordinary phones" there is a fugitive window which appear for 1/4th of seconds and then i get the message telling me to enter the number in the dialogbox. Bug ?
We cannot call a contact which is not yet in our contact list (I only tried with "echo123") this is useful when making a first call
on the bottom on the window, the number of users connected is 0, I guess this is a bug since skype is very proud to announce anytime a new million is reached
When no contact is selected, it would be nice to get a right-click menu when clicking in a blank area of the contact list like "add contact, call phonelines, options, ...)
In the options menus :
notifications tab, the feature execute a script on event is very nice ! (I already made scripts to play/pause amarok when incoming call and ending call events). However we have to fill ourself the path to the script, a little button to open a window and browse through our files to select the script would be nice.

. For the rest of this Notifications, don't change anything, the "test event" is very useful to test my script

Sound devices : "make a test sound" button is greyed... whatever the sound device selected is.
Hope that helps.