I think Solidcoin made one great change that makes it viable for a secondary market for BTC. While I don't currently anticipate a new coin coming out that becomes a viable currency for online stores, I do think SolidCoin's difficulty retarget method makes it a tool for non-USD BTC exchange.
The 10% limit on growth while maintaining the 75% fall in difficulty on a 240 block/12 hour window means it is immune to what happened to I0C/IXC, where the flood of miners hit the currency and vanished when BTC became higher valued.
Whether or not the speculation secondary market can survive can't be predicted, but at least SC had the right idea when it came to difficulty readjustment period for a competing/alternate cryptocurrency.
So you gonna point a giant pool at it for testing purposes or no?
We already have the largest pool, though we're under 50% unlike i0c where we definitely passed 50% right out of the gate. If we start solving 60 out of the previous 120 blocks I'll probably close registrations. I like the idea of a currency which can maintain a steady trade rate with BTC outside of physical "real currency".