It's hard to give a strait answer without knowing more about the project but, having worked on web development projects from the developers end, I guess I'd have to ask a few questions before I gave feedback. Kinda playing devil's advocate here.
Did the scope of the project change? I have worked on projects where the scope kept continuously changing, and it's frustrating from the development end because it continually sets other things back, or forces the entire project to be rearranged. You can't actually finish something that keeps growing, and changing.
I doubt this one is an issue, and it may be touchy but, did your developer receive a deposit or any sign of payment? Having worked on projects that kept growing with no monetary value in sight I can say from that perspective it doesn't encourage one to work a pace, if you know what I mean.
Not intending to offend, but a project becomes a developers dream when they have something invested in it.
Does your developer, in fact, have everything they required for the project to be completed? I've had multiple instances of a client wanting a finished site without providing me with everything I need to present a finished site. If they say they have everything, then there is really no excuse not to have it done unless the two options above are an issue.
If none of these is an issue, I would let them know you want to see the final version by a certain date and if they don't show, then transfer the project to another developer.