It's not bad for free software. If you're spending somebody else's money or making a respectable living diddling with databases then get Navicat: it's significantly more powerful.
Now I know - there will be responses to this.
Honestly, phpMyAdmin in my opinion is only great IF you need to share access to your database servers. Outside of visual ques I am not really sure what the advantage is of using any GUI applications over command line.
(Other than the nice ability to use ctrl + v / ctrl + p lol)
Anytime I have used something graphically to save time - in the long run - time has been wasted with a poor performing query.