Let me state my opinion on this:
For the improving beginner, I think blitz chess (if done regularily) is an awful idea.
I think if blitz is to be done for a beginner, it should be 10 0 - and rapid/slow would be much better.
If it is the only option for improvement, no slow games or chess books are available, it's probably better than nothing.
(especially if you use it to get better at openings or tactics - but if you aren't, how could it really be counted as useful for improvement?)
the real question is what will provide more improvement per unit time: blitz or classical?
How many times do I have to keep repeating myself?
I wrote in my first sentence that the best way for a beginner to improve his chess game is to play 30/0 games.
Why don't you read what I wrote?