Trade up from D3 to D800?

I'm contemplating moving up(?) from a D3 to a D800. Values on the D3 still seem decent, just a few hundred different.

I'm curious if anyone has made the switch, why, and what you miss on the D3.

Some bkgd- Prior to the D3 I shot an F4s, and honestly very little for the 6-7 years prior. I'm using my current setup mostly for architecture (I'm a structural engineer, and getting good marketing shots is what I use it for, with a 14-24/2.8 or an old 35mm t/s) and for theater (I'm on the board of a local theater company).

What bugs me on the D3 is the lack of dust control on the sensor. I know that seems trivial, but coming from film it's a bit of a thorn. Sure, I can spot heal in LR, but it's a pita.

I rarely use > 6fps, usually 3 or 4 in Cl mode, so I'm not sure the loss of speed will matter.

Video is novel, but I'm not sure if I would use it much.

I will say that, after years of LCDs, I would welcome a more functional live view. I find the OVF limiting at times. On the old F4s I could pop off the pentaprism if I wanted a quick low ange shot and just use the glass.

Thoughts on if this is just $500-1000 flushed away, or has the 800 really made a difference for you.