I love panels.

I do not use my GroupWise without panels. Therefore I assume that you use it in the wrong way.

You have mentioned that you have created a panel pointing to folder Mailbox. The new panel shows what is stored in Mailbox. However did you consider that Mailbox does not only contain inbound mails but outbound mails too.

To keep it simple for most of our users Mailbox shows only incoming mails. And 'Sent Items" shows only mails that you have sent. Nevertheless both kind of messages are 'stored' in Mailbox. Smart filters help us to see it in different folders. If you create a new 'view' (=one of your panels) and point to folder Mailbox then you will see all of them at once - except you use filters ...
 

There is so much power in panel views. I tell my power user how to use it!

I love panels!

Panels can be used as Diethmar pointed out for a lot of things i have seen customers in sales using a folder ( for each customer a folder) that was setup as panel with  columns that had received and send items with the filter for that specific customer so easy to see all communication.. also panels can have a URL defined so also this was used to have a dashboard next to items.. in a way you can based on views/filters/panels per folder customize a lot for the job you do... 

When like me only sending and receiving mail and sometimes an appointment its less usefull but many power users in GW have found great ways of using this

I'll give you two examples.

The first panel has four fields - always pointing to the same folder Mailbox. But you see different contents because of filters.

My second example is more useful 

What do I have to do today, this week ... which tasks are overdue ...

OK, thanks much. Works great. User is happy. I can see where filter options give users lots of power.