I find it better than Heaven because Hella sounds like a nickname for Helena. Just forget about the spelling for a moment and you will probably notice it does sound nicknamey. In the English-Speaking world this name is unusable as a real name but as a nickname feel free to use it.
This name is also used in the Netherlands and the pronunciation is the same as the German one. A famous bearer is Hella Haasse, a very famous Dutch writer.
Well, I guess it would depend where it's used. It could be okay in some other country, but in the United States, if you had this name, you WILL be bothered. And the way the US schools are now, you will be completely miserable.I do not suggest this name in the United States. (I'm not being racist, because I am a US citizen, and I'm in middle school, so yeah)