When I joined this forum I had MyGlam and was waiting for my first BB.
I now have:
Monthly
MyGlam
TWO Birchboxes (TV box mania! lol)
Beauty Army
Julep Maven
Sinduldge
Quarterly
Beautyfix
and possibly Test Tube (both QVC and the regular one) when I can.
My favorite beauty boxes, so far, as I haven't received Sinduldge yet, are Birchbox (love the points, love the store, love the customer service, going annual soon) and Beauty Army (great sample sizes, excellent customer service, fun Facebook wall). MyGlam started off strong, I haven't been upset with them at all, but they can stand to have better customer service. Customer service makes or breaks a company for me.
Julep Maven is fantastic and I will keep it because I can skip a month at any time, they have stellar customer service, I love the extras, and I can switch styles if I want. I don't include it in my fave beauty boxes as it's a nail polish box. I love it and it's not going anywhere.
That said, if I could only keep one thing out of everything I subscribe to it would be... BEAUTYFIX! Funny enough.
With Beautyfix I got almost all full sized products (the deluxe samples, that were truly deluxe, were of super expensive things) and the value of my box tripled what I paid. I, personally, (I say personally because this was not the case for others) had great customer service. I get to pick what I want and they have a lot that I want.