The small "passionate" market is just that - small. I have subscribed to a few of these mags over the years, but with rising costs of subscriptions and the content not capturing my imagination, I've let them slide.
That's not to say they aren't great magazines, but for me, the cost vs content of interest just wasn't there.
Maybe I'm one of the minority, but I like a good variety of articles in my mags (regardless of the subject) and when I find that them starting to wander away from my particular interests, I let them fall by the wayside. (I have always let the subscription finish - never cancelled mid way.)
Mainstream mags have the edge in that they have the staff on hand to cover a multitude of topics - the more "niche" magazines don't and I have found that the content can sometimes be too narrow in subject matter or just not of interest to me at all.
I subscribed to Silverprint for 3 years, but cancelled when the cost went to $20 an issue and the content just began to showcase photographer's work with very little else to fill it.
As I said earlier, I like a good mix in my magazines - regardless of whether you are a "niche" or mainstream photo mag, if you cover these areas well for my tastes, I'll be more than happy to support you.
But for now, I haven't yet found a "Passionate Photo Magazine" that fills my requirements. At this stage, it's the mags in the business of making money that are getting my $$ - good or bad, the "Big Business" model is winning - hopefully I will see a "Niche" mag take over my subscription $$ soon.