Tempo is the purview of the host. The next version of reViSiT (v0.87.2) will include a new Axx command, which will control RESOLUTION. It actually works similar to the old IT2 Axx command, in that it sets the number of ticks/frames that are executed per row. The difference comes from the fact that IT2 kept the number of ticks per second constant and reViSiT keeps the number of rows per second constant (to make the host sync. process more logical). Because of this, the IT2 command will change the SPEED of pattern playback. The reViSiT one will not. However, this new Axx command will make it so that old slides (pitch, volume, panning) are all compatible with your old tunes. The only thing you might have problems with is looped samples. In any case, all you have to do is change the tempo of the host to compliment your old Axx command.

As for the sluggishness you reported, it could be due to the graphics and it could be due to the keyboard handling. The next version of reViSiT will add WIN32 mode handling for EnergyXT, so you'll have to let me know if this improves anything.

All the best,
Chris