DDI is a great deal for me. The compendium saves me hours every month in prep time - that alone is probably worth the price. The character builder is great (I felt no need to buy Arcane Power). The magazines are quality stuff (though Dungeon needs three adventures a month, not two, and the AP just isn't a path that is well thought out). Everything else is bonus to me.
How many companies that you deal with say "hey, this introductory price is about to increase. Tell you what, we'll let you re-up at that price". Um, none?
It's not perfect - the big black bar needs to go; we need to be able to copy and paste from the compendium and keep the formatting; Dragon could use a few more articles, even short, usable ones for PCs; as I said above, Dungeon needs another adventure every month; I'd even like more plug and play encounters.