It would be nice if Code insight inserted on tab key either only the smallest shared part of found code variants or separated variants by a separator.

example: when using Zend Framework, to insert Zend_Controller_Action_Exception I have to write "Zend_Controller_Action_E" or scroll vigorously in the list of classes.
When inserting only underscore separated parts, i'd have to write only Ze<tab>_Cont<tab>_A<tab>_E<tab>, which would be much faster.

If you have code completion on tab turned on and a high delay on your popup window, you can achieve what you are wanting.

It works for me anyways...

It really works, thank you very much!

Anyway, this feature would be even better with popup window preserved

Well, not really. I use PhpED 5.5 buid 5518. When I type ze and press tab, it gets Zend_ (which is OK), but no code insight popup window is shown after that (at least in my case). That's quite a killer for code completion. It means that you can use either code insight or code completion but not both at the same time. I know that there is a shortcut to display the code insight window, but that's a pretty uncomfortable way. I don't see any reason not to display the code insight window automatically after using code completion.

The second problem is that you cannot use code completion when the code insight window is shown, because hiting the tab key selects an item from this window.

I would really, really appreciate if:
the tab key was used only for code completion,
the code completion worked even if a code insight window is shown,
the code insight window appeared automatically after using code completion.

I agree with you on one aspect.
The tab key should not select an item from the intellisense window.

You can assign a hotkey to pull up the intellisense window (very quickly), so I don't see the need to pull it up automatically.

I don't think this is a comfortable way. Every developer I know tries to reduce number of keystrokes to minimum. Hitting a hotkey (by default, it is alt+space => two more keys) is minor, but still a hold-up in work. I, on the contrary, don't see a reason why not to pull the code insight window automatically (and I belive, to ensure everyone is satisfied, that this option could be turned on/off in the settings window ).