[Product Question] Anyone test the results of shower head filters?

I am wondering if they work or if it is just a placebo. Obviously we all have different contents in our water depending on location. I'm considering purchasing the AquaBliss filter, but I don't think it's worth it if the filter doesn't work or needs to be changed so frequently.

I have seen comments with concerns about the water passing through too fast to have enough effect and chloramine clogging the filter. Also, there is the concern that these smaller filter do not soften the water but rather reduce small amounts mineral content.

Anyone run tests to see if their is actually a difference? Do you think that they are worth it?