If you're building a budget system, a d8xx series cpu will serve you well.
80$ is not bad for the 3Ghz model, but considering that a d805(the easiest to overclock in that family) is routinely available at 90-100$ nowadays, it's no ground-breaking deal.
If you already have a MB that only accepts p4s and pentiumd Ds, and you're upgrading from an older pentium (or god forbid, celeron), then I'd say go for it.
If you're building a new system, I'd recommend you save up a little more (or wait a few months for the price drops) and build a system based on an E4xx, those will be priced well under 150$ (after the price drops). The current low-end E6300&E6400 will be given 4Mb of cache, and will be priced <200$, making them a good choice for a budget build as well, whether you OC or not.