D&D traditionally has been a very magic item (equipment) and spell oriented game. Characters are severely weakened without their equipment. Spells can simulate or do better than proficiencies or skills.
If you don't want equipment to define characters, can I recommend giving the players faster progression of ability points and skill bonus feats to cover this gap. e.g. You could give +1 to an ability every 2 levels, or even every 1 level. To limit power creep, you can limit how much of a bonus can be added to a single ability (e.g. +6). Similarly for skills, except the mechanic I would use would be to give out skill focus feats periodically - say 1/3 levels at 2nd, 5th, 8th, 11th, etc. This places the maximum skill bonus to an ability (+3), but does help mitigate the lack of skill items.
For my high level Rogue-type character, skill items are essential. He doesn't have enough skill points to go round - the skill items help fill the gaps. It would be less of an issue if he only specialized in say Hide, Move Silently, Disable Device, Open Lock, Search, Listen and Spot. However, he also makes a fair bit of use of Disguise, Bluff, Diplomacy and Gather Information ... so too many skills to be excellent in any one skill without help.
With respect to my second point on spells ... keep in mind that skills like Balance and Jump are completely meaningless as soon as the spellcaster can fly. Alter Self, a 2nd level spell, enables flying. Most skills are really very weak abilities compared to combat abilities. It doesn't matter if someone gets +10 to these sorts of skills (e.g. the Jump spell). There are a few skills that are very useful in combat: Concentration, Tumble and Use Magic Device spring to mind. I would be much more cautious about allowing items that give a significant bonus to any of these skills.
Compare the current magic items to AD&D. In AD&D, a Cloak of Elvenkind gave 99% Hide chance. Compare to spells: cast Invisibility - who cares about Hide now ... well, okay we do, because of the 3E rules, that the spot check is only DC 20 ... but you get the idea ... the 3E rules are better, but spells still completely outdo most skill powergaming options.