EL in ZK 6 I had some issues trying to figure out some basic stuff since I didn't see it documented anywhere.

For concatenation I seemed to have to use el2's concat function...

view plainprint?

1. <listcell label="@load(owner.lastName.concat(', ').concat(owner.firstName))">  
2. </listcell>   

For equals you can't use == , need to use el's 'eq' or 'ne'

view plainprint?

1. visible="@load(productGroup.owner.id eq user.id)"   

visible="@load(productGroup.owner.id eq user.id)"