Is 4K good enough to choose for special footage such as weddings?
Where are you planning on exhibiting the footage? In my experience, the average consumer has a low-quality TV they bought because of the price, and they have the factory settings that look awful because they don't even know that they would want to change them, let alone how that would happen. In my opinion you're wasting your time because your client probably won't be able to tell the difference.

On the creation side, you're multiplying the amount of data captured by 4. That increases the cost of filming (more memory cards to save it), storage (more hard drives to use while editing), and editing (need a better graphics card, more RAM, and likely more time). 

If you have clients who will truly benefit from 4K, by all means, use it. But if you're doing typical videos for the web, corporate or home televisions, it's probably not worth it. If you're creating content for large outside displays that actually reach above HD, or for professional projection in a theater, then it could be worth it.

FWIW, most television shows are shot in HD, and even some feature films. I've never heard anyone complain about the quality because of the lower resolution. If I recall, parts of the first Captain America movie were shot on a Canon 7D, which only does HD. I know of nobody who said those parts were terrible or even noticed them. (Here's an article about it on Canon's web site.)