A lot of guys preach it as the cureall in a relationship and while it can be effective, it can also be incredibly dangerous.It's a specialized tool that you have to use cautiously. It's essentially a relationship A-Bomb, threatening her with the emotional devastation she'll feel if you break up. A list of guidelines to consider before considering the U-Bomb.
Don't use it too soon. After two weeks you're not close enough to inflict any damage and she's likely to think you're demanding, oversensitive, not worth the hassle, and a total jack@ss besides. And she's right.
Don't use it too often. It's loses some of it's effect after the first time, but if this is the third time in the last six months (or worse month) that you've threatened her with the aforementioned emotional devastation, she'll weigh the stress you're inflicting versus the stress you're threatening to inflict. She'll likely think you are demanding, oversensitive, etc., etc. Besides which, if you have to do it more than twice in a relationship you need to either work on your communication or find another girl because it's obvious something's gotta give.
Don't use it for anything trivial. Proposing an all or nothing scenario because she denied the dirty dirty once or threw out one of your CDs makes you the d1ckless wonder and shows her exactly how little you actually care about her.
Use it only as a last resort. It's never the same after you use it because they are now consciously allowing for the possibility of you dumping them outright. All sorts of defense mechanisms can kick in and frankly, it could take a while for trust to come back.
Lastly, only use it if you mean it and are prepared to accept the consequences of the U-Bomb. If life hurts too much without her and the knowledge of her complete unwillingness to bend your way isn't balm enough you never should've dropped this one. Reneg, and you will never recover your happiness, or your masculinity.
-CyranoDeBergerac