On one hand, the ore processing line requires a block of diamond to set up, not to mention a stack of silver to get enough power, and a stack of lead for the heaters and motors.
On the other, the ore processing line can get you, I think, 2.2 diamonds (on average) per diamond ore without messing about with implosion compressors. It also yields 3.5 coal per coal ore, which is insane. That said, the crystallization phase (for metals) is inherently very slow, and the mixing phase is quite tedious unless you figure out a way to automate it (probably RP2 would work best there).
That's leaving aside the wrath lamps and routers, which are certainly interesting in their own ways.
Really, factorization is rather underappreciated, I'd think.