I think I will chime in on the necessity or lack thereof of the secondary items...
I don't think the idea behind secondary magical items is that they somehow do not increase character power. After all, having something is always better than having nothing unless the something is completely useless. A character who has secondary magical items will be stronger than a character without secondary magical items. However, the important thing is how the former will be stronger, not whether he is.
I imagine that a lot of secondary magic items will provide situational benefits, compared to the "always useful" benefits of the primary magic items and the old 3E "Big Six". Powers like water-breathing, flight, or darkvision are all situational benefits. Darkvision is useless in daylight, but great underground. Flight is useless in a cave, but great in open areas. Water-breathing is useless on land, but invaluable in a flooded cavern. These kinds of abilities are certainly useful in certain situations (or even many situations), but they are not the kind of abilities you need for every fight in the game, no matter what, like attack bonuses or AC. Items like this are among the most fun of the magic items, but were cast aside by the "Big Six" of 3E. One of the great advantages of the new system is that it encourages using such items, rather than discouraging them by providing obviously better alternatives.
Anyways, the thing about items with situational benefits is that they are the kinds of things that they are never completely necessary. If you need to fly, you can find a pegasus, hire a dragon to carry you, or even find an airship. If you need to breathe underwater, there may be magic rituals to let you do so temporarily or you can just choose a race which has that ability. Darkvision is similar. Finding an alternative to a secondary magic item is incredibly easy compared to adjusting the math to make up for a lack of primary magic items (which is not all that hard itself in 4E).
Because of this, while a single PC who does not have secondary magic items may be weaker than his ally who does have secondary magic items, a group of PCs who do not have secondary magic items can still get through a campaign just as well as a group of PCs who do have secondary magic items, simply because there are so many alternative solutions to the kind of challenges that can be overcome by those kind of items. Secondary magic items really are optional for campaigns.