The Page Designer makes you way more productive, less clicks and quicker results. You have to get used to it, and you probably want a big monitor (time to ask your boss!), but once all that is done - you will love it.
The Page Designer is so intuitive and attention was put in the details. When you make a mistake APEX gives you immediate feedback. Here's a screenshot:
The region where the error is, is highlighted.
You get a notification message top right in red with the error message and inside the property panel it's highlighted what you need to change. Once you click on the field it will give another text notification e.g. that it is required.
There's also the Messages tab which gives you an explanation of what is wrong. Clicking on the link will bring you right where you need to go.
But just look at the Page Designer for a while; notice the small top left red triangles; it identifies it's a required field. The "Show Common" and "Show All" tabs are great too.
So many things, small, large, ... but so useful.
Here's another one - Developer Comments for the page. If there are comments you see a number in the comment icon. When clicking on the icon you can add more comments. I believe it would also be useful to see the existing comments, hopefully that will be in the final release.
This post is based on Oracle APEX 5.0 EA2, but there's more coming it looks like. Linked to the previous feature, I see a tighter integration with Team Development already too.
So many things to explore in the APEX 5.0 Page Designer... definitely worth your time.