I just dumped Starz and Cinemax as Netflix has much better choices, at a lower cost, and in Blu-ray. I can also watch them when I want. I would dump HBO and Showtime too if it were not for their original programming.
With that mentality, why not just wait for your HBO/Showtime shows to hit DVD and cancel them too. Doesn't Netflix rent these series? I know you can buy them on DVD, so you should be able to get them from Netflix.
In my opinion, HBO is a real bastard in taking away good series. Lucky Louie was so refreshingly good. I cherished season 1 and longed for a second season. HBO canceled it. Carnivale was a good show too and could have come back.
I am mixed on Showtime. I haven't really fallen in love with anything. I like the Penn and Teller BS show. That is on Showtime, right? or is it HBO.
The bottom line is, just about everything eventually hits DVD. One could get rid of all premiums as you did Max and Starz, if all they wanted was the series.
I keep all the premiums around for those hidden gems that I would have otherwise not found (movies).