i've used close up filters with respectable results
even the really amazing macro shooters use them sometimes (in addition to their macro lenses)
optically, they're not great...but most of the affected quality is around the outside
i have the tiffen set, they stack...but IQ really sucks when they're stacked
i just use the +4 one
a lot of people swear by the canon 250d (i think thats the canon close up filter)