Helm is terrific. I switched to it from ido in the past 6 months and it's really increased my efficiency. In particular helm + projectile allows me to really quickly switch between projects and navigate to the file I need. I remapped some of the most-used emacs commands to their helm equivalent's and haven't looked back:

  (global-set-key (kbd "C-x r l") 'helm-bookmarks)
  (global-set-key (kbd "M-x") 'helm-M-x)
  (global-set-key (kbd "M-y") 'helm-show-kill-ring)
  (global-set-key (kbd "C-x b") 'helm-mini)
  (global-set-key (kbd "C-x C-f") 'helm-find-files)
  (global-set-key (kbd "C-c g") 'helm-git-grep)
  (global-set-key (kbd "C-c C-.") 'helm-git-grep-at-point)
  (global-set-key (kbd "C-x C-d") 'helm-browse-project)

My one complaint is getting used to C-z to drill into a directory when navigating the file system with helm-find-files. I haven't et figured out a way to map RET to do anything other than open the selected directory in Dired.