There is still a bug in the printmodule. I have reported this earlier for LR3.3
Using custom package, and choose a border ie. on 20 pt. The preview look perfect, but on the outputted image, 20 pt is missing.
This may easily tested by just using a file as a print destination.
I miss a working border function!! As this works now, it is useless.
Borders seem to work fine for me. Keep in mind, the borders are always white, so if your page background is white, you're not going to see the border (unless two photos are overlapping). The black edge that appears around the border when you view it in Lightroom is just there so that you can see that you've applied a border. If you want a colored border, use the "Inner Stroke" feature, and the color of your choice.
The problem is not that the border is missing. The problem is that part of the image is chopped away. I may be more visible if you set the border to max size: 36 pt. Compare the preview with the print. I have also turned on "cut marks", so I can see where the border is. I would be surprised if you get the same image area on the print as you see on the preview.
Keep in mind that this problem applies to the "Custom package".