Examining execution plans is the key to improving query performance.  The knowledge and experience necessary to look at a query plan and say "yeah, that's where it screwed up" and fix it makes all the difference in the world.  I'd submit that query plans are one of the single biggest tools in a DBA's toolbox for fixing performance problems.

So why does the UI suck so bad?

I just pulled up a query plan for a fairly complex query.  I can't find the problem.  Why?  Well, across the several hundred steps, I can't see anything that's not taking 0% of the query time.  There's no search feature.  There's no ranking feature.  Here's a feature suggestion for the query execution plan screen: When I hit ctrl-F, let me search for things.  And add a new hotkey to take me to the node in the query plan with the most cost, then the next most cost, and so on.

I could print it out and look that way instead of scrolling (A new feature in SQL Server 2005, before we had to printscreen.  yeah, printscreen) but it would take 165 pages.  And most of those pages are BLANK.  And there's no option to supress blank page printing. The first page is literally a line across the middle of the page with 3 nodes on it.

OK, I have to ask.  Is there anyone that does usability testing on the SQL Server development tools?  Seriously.  Anybody?  Does Microsoft invite a couple of DBA's, even some SQL Server MVP's, up to Redmond, sit them down and ask them to do things with the user interface and watch them?  Why not?  Throw them an invite, buy them a plane ticket and have them sit down in front of a computer and look at query plans, print them, and try to do their day jobs with the tools you've provided.  Gah.  At least get a couple of people from the Office team come over and show you how to make a UI.  This thing's abysmal.

Yes, I know that the SQL Server tools are the best of the tools that ship with any DBMS.  That's like saying you've got the best congressman though.  News flash: The best turd in the world still stinks.  Stop playing to the level of your miserable competition and start playing to the level you want to be.  Being the best in the industry isn't good enough if the rest of the industry is writing smelly poo.