As I see it, enchanted items are not only handy in some specific situations, they can pack a real punch if you know what you are doing.
For one: 1 focus item slot can translate to a 3 uses enchanted item, which will come in real handy in long fights, because it does not use up your mental stress track. Then there is an optional rule, that lets you convert +uses into +power on the fly (or was that a house rule?), so if you need to, you can really bring the pain.
Also, enchanted items can hold thaumaturgy spells, which means you can store spells of elements you don't have in your evocation repertoire and thaumaturgy-only effects like skill replacements to cover some of you shortcomings in other skills.
Focus items are good to cover a gap between conviction and discipline, though I prefer specializations for that, they are more reliable. If you have your casting skills evened out, you can use focus items to boost your casting powers a bit, depending on your preferences.
I think a good mix of focus items + enchanted items + potion slots is the best way to go, if you are not looking for a specialized build. Focus items to boost you signature spells, enchanted items and potions to have a well rounded toolbox/arsenal. If you are going for a specialized build, everything can change again, depending on what you are planning to do.