It's a stunning grid control and there are some tips to getting it to work properly.
We used it with ado data (the only real way) but it is very slow with very large volumes of data and can become unstable in these cases.

We have used it quite a bit on vfp 7.0 and 8.0 apps.
The same code in VFP 9.0 generates one of those C0000005 errors and crashes foxpro, however we have not had the time to investigate this.

I think the fact that ultragrid works with vfp is more coincidence than by design as it was not designed to be compatible with the VFP event model.