I personally think that blitz is good for development. Not only has my blitz rating gone up 100 points over the last few months, but my standard rating has progressed similarly. And this improvement has mosly been made by playing blitz games.
are Blitz games good or bad for developing chess skills?

If blitz didn't help your chess skills, I have wasted a whole year.
Seriously though, blitz has pros and cons to it.
Some pros are:
-Quick tactical ability
-Teaches to play fast
-Trains intuition
-More fun than long chess
-May give pyschological edge if your opponent is thrown off by seeing you play fast (happened in a real game to me)
The cons are:
-May cause players to play too fast, and make blunders that would probably be overlooked in a blitz game
-Calculation ability is neglected
-Hard to follow/make subtle plans, or extracite tactical blows, just basic stuff
I'm a blitz player, so I prefer blitz, but really, its your weakness that decides. If you have problems with time, than blitz may curb that. If postional/tactics are your Achilles heel, than long games may be better to make you sit down, and actually calculate, rather than use your intuition.

I knew how to play chess and played in high school. I understood basic tactics like avoiding forks, uncovers, the 5 move mate, trading pieces, backing up your pawns, pawn chains, etc. I am about 1500 blitz games (3/0) in, and am improving rapidly. My mind works well with blitz. Now I can recognize openings, I rarely hang a queen, and am just moving up in ranking. While it may not be as good as standard chess, for those of us who need to get games in in a 5 min window (I.e. waiting for my wife to get ready in the bathroom) its perfect. I still argue I am a way better chess player than ever. And I find that the stupid moves happen less, even in blitz.
The lower the amount of time, the higher the unpredictability, so blitz/bullet games should be used to strengthen your ability to handle time pressure and your pattern recognition.
They can be fun sometimes, but you can also lose to someone rated 600 points below you.
It is also used by strong players to reinforce their memorization of their opening repertoire.