I really like the Pianist magazine which I have posted about here. Yesterday, I did a little google search for other keyboard/piano magazines and discovered Clavier Companion which I think has only been in existence for a little while as there are only 9 issues dating back to 2010. It is perhaps aimed at the more experienced pianist being a little more erudite than Pianist with some great in depth analysis articles. Like Pianist it is published every 2 months and they also offer an iPad app. Although, their website offers a digital edition to subscribe to it appears that if you use the iPad app you can download the issues for free as I have done just that. with 8 of them. Do check it out as I think you will find it is well worth it.