And yes, you can use the "Edit In" feature of Lightroom to open a rendered photo (in PSD, TIFF, etc format) right in Photoshop Elements Editor just like full Photoshop. When you save the photo and return to LR it's in the catalog as another version of the original, and you can even do LR editing on top of it (but opening it back in PS makes more sense to me). The nice thing is you can export, watermark, print etc the PSD/TIFF right from LR just like RAW/DNG files you've edited in LR natively. Very seamless.
A PS instructor at our University told us Elements was released as a light version optimized for photo editing, so what you mainly loose are some of the exotic design tools. I think LR 4 + PS Elements 10/11 is a killer combo.
So you can export into elements. I guess LR automatically detects another Adobe product. I never had elements so did not know how to answer that one.