Just changed my oil. I picked up a Dimple as well. I think their pricing is almost ridiculous, but at least it seems like a good product and I couldn't find a great source for other BMW compatible magnets.
Here's their plug compared to the stocker I pulled.
No issues getting the new Dimple plug installed. Note some of the height difference is a taller head, but there are about 2 extra threads of length as well.
Not much else to note. It was an oil change job. Once I'm due for another change I'll post a picture of the plug.
I'm not entirely sure drain plug magnets are a huge deal in car engines, either. The filter should do its job. If you are paranoid you can always change your filter between oil changes, too.
I use this filter, only $9.14 shipped with Prime:
http://www.amazon.com/gp/product/B001DRHMRI
I use this filter wrench as well, works great:
http://www.amazon.com/gp/product/B000XML6DU