Gawd, this SUCKS!
I've got dozens of issues of both Dragon and Dungeon extending nearly to the beginning of both magazines, and after 25 years of playing D&D, I finally subscribed to Dungeon last year. The loss of these magazines leaves a HUGE hole in the shared D&D experience. It also removes one of the last reasons I had to visit an FLGS.
Speaking on Dungeon particularly, there goes the best deal in adventure gaming. And we also lose some unique benefits of its adventure format. One of the great strengths of Dungeon was its publication of multiple shorter adventures. Being easier to write than the full-sized standalone or campaign-length adventures Paizo will be doing now, the format allowed for the discovery of great freelance talent over the years. Many, if not most, of today's best adventure designers started in Dungeon magazine. How will those new talents be discovered now? I don't believe online distribution of shorter adventures will generate the exposure of a single industry-wide print publication, and which may be crucial to honing such talent on a demanding stage.
The shorter format also allowed for experimentation that longer formats don't support, I believe. Could you imagine someone publishing full-sized versions of adventures such as "Diplomacy", "Swords of Dragonslake", the "Challenge of Champions" series, "Siege of the Spider Eaters", "The Palace of Plenty", "The Coming Storm", "The Prince of Redhand", "The Obsidian Eye", or "Box of Flumph", to name some from the last few years? Even if someone published a full-sized adventure with elements similar to those in the aforementioned scenarios, it'd be more expensive, and you wouldn't get the thrill of two MORE adventures of totally different styles.
Finally, with no magazine carrying the imprimatur of "Official D&D" from WotC, there go all your Eberron, Forgotten Realms, Greyhawk, Ravenloft, Kara-Tur, Planescape, and other adventures, except for those that might be published by WotC itself.
Sad news.