I'm really happy I bought the grow light. It's made an incredible difference in seedling quality. Last year's seedlings were thin and leggy, this year's seedlings are much stouter and bushier. The difference is very clear in the pictures below.
Nice, thick stems and full, green leaves. You can see the roots starting to spread throughout the cups.
They're growing quickly, I might be forced to pot up again before they go on the roof, something I had hoped to avoid. I've stopped feeding them fertilizer, maybe that will slow their growth. My timing is off, I clearly underestimated the effect the grow light would have on the seedlings. Next year I'll start seeds at least a week later.
On a side note, 2 Atris pepper seedlings I thought had died of damping off actually survived and sprouted new leaves! This means I'll have 4 seedlings to plant on the roof. Yay!