I like to use my DMG for alot more then a list of magic items so yeah I would like it at the same time as the PHB.
Environment effects, quick npc stats, status effect summaries, traps, helpfull brainstorming suggestions by just rereading a section I haven't looked at in a while, I try and use it before every session to make my game more interesting, with what I hear about 4E's possible use of Iron Heroes encounter zones I think I will use it even more.
So yes I am very happy to hear that all three books will come out at once, and with 5 months to set alittle aside for the whole set after Chistmas I don't see any issues with buying them all at once, thats like what 100 dollars or so spread out over 20 weeks, 5 bucks a week doesn't sound to hard to put in a 4E savings jar.
Plus I think I might just put gift certificates to my FLGS as a priority for Christmas gifts this year when people ask me what I want, that way I can preorder them and not worry.
Ohh and could I make a suggestion to the fine folks at Wizards, some of the guys here are the most loyal fans of the hobby and are very good at combing out errors, prof reading ect, not because they are payed or it's their job but because they love the game. Before sending off the final copy to print send a pdf or something to Eric, Hypersmurf, Orcus, ect like a week before any final changes need to be made, put them under a NDA. You will have a 99% errata free product after that and it would be a good way of showing some love to fans who love the game so much.