Yes, I've been there. I've heard many a strong player say Blitz is to Chess what McDonalds is to food. Others believe your playing strength drops 300-400 points if you are blitzing and your opponent is actually using his clock.
The few useful advantages of blitz are tactics training and opening practice. Even then => Blitz with a tournament-friendly time-delay like 5-5 (as opposed to 5-0). This way, you are also training for time-trouble moments in tournaments (assuming you play them) and helping keep your nerves steady.
this topic is probably way overdiscussed, but I have been wondering about it. I've been taking an interest in blitz and bullet games, and learning to move quickly. Now I've noticed that on my turn based (longer) games, that I am making more blunders and not taking the time to truly evaluate my position. Anyone else having this problem?