What do I lose if I move to DD-WRT?

Hello

I just got the RT-N66U and am contemplating installing DD-WRT firmware. I came from a Linksys (E2000) which had DD-WRT because the stock Linksys firmware just didn't include sufficient features.

The N66U seems to come with a lot of stock features built-in which seems to do what I want so I'm wondering what benefits/added features I would get from installing DD-WRT?

Also, what features would I lose if I went from stock to DD-WRT? I'm guessing the ASUS features like AiCloud and ASUS DDNS would be gone (or are they still supported in DD-WRT?)

Any comment is much appreciated :)