I'm really looking at one of these. My Mom is looking for a cheap laptop and if I can upsell her on one of the bigger Dell's I'll piggy back on her order for the $99 deal (I'll give her $150 or something to offset the cost on her laptop order, plus extend her my government employee discount).
I give it about a week before the OSX86 guys have Tiger on this.
It's based on the same platform as the Acer Aspire One/MSI Wind etc, and Leopard's already working well on them.