I've personally done this a few times and I'm quite inexperienced weh it comes to LDing. It's not the actual re-entry that's hard, it's remembering not to open you eyes or move when you wake. Usually the first thing I do when I wake is roll over so that's the toughest part for me. I haven't tried this for a while now that I think about it...I should get back into it. Usually it's the only way I can make myself lucid. Most of the time it's random chance. Anywho, that's my input.