CS4 can do focus blending with Auto-Blend Layers. You might want to Auto-Align Layers first. Not quite as good as some others, but OK for many things. IMHO none of the focus blending programs really works as good as one could hope, ghosting around nearby objects can be pretty severe in all of them. Minor focus offsets like from the infinity and 30 feet work fine, but infinity and 2 feet is always unsatisfactory (even if you have lots of intermediate focus points). Combine ZP (and probably others) can generate and save intermediate masks that can help you touch things up a bit, but that's a big job even with the masks.
For landscape work I usually prefer two or more auto-aligned layers, blended together with a soft edge masks. I have noticed that PTGui with usually do the right thing focus wise with two-row stitches where the focus points in the top and bottom rows are different.
Edit...and also for blending multi row landscapes with different focus points CS4's Auto-Blend works great when applied to panos brought into CS4 as individual layers, it seems to actively apply some sort of sharpest layer rule when blending.
