Installing just Haxchi is perfectly safe and will give you simple channel access to other homebrew programs without the need of the browser exploit anymore.
Installing CBHC though is FAR, FAR more dangerous but will allow coldboot into patched menu/homebrew, read this for more information:
Changes to CBHC:
-added vwii boot option to cbhc
Changes to CBHC and Haxchi:
-made installer more stable on exit