On the other hand Clearcase dynamic views were pretty awesome. You just needed to edit your view config spec and the view FS would render the right file versions immediately. No checkout required. There was even view extended naming to let you open multiple versions of the same file directly from any editor.
As for merging Clearcase set the gold standard for three-way automatic merges and conflict resolution that wasn't matched until git came along. It's still superior in one important way - Clearcase had versioned directories as well as files so you could commit a file move and someone else's changes to the same "element" in the original file location would be merged correctly after the move. No heuristics, just versioned elements with versioned directory tree entries. Backporting fixes was a breeze, even with a significant refactor in between.
Git more or less wins hands down today because it is fast, distributed and works on change sets. But something with git's storage model, a multi version file system and Clearcase's directory versioning would be an awesome VCS.
