I've got a triple-chip Freud on my table saw, and it leaves a pretty
flat bottom on the kerf. If you're not familiar with the triple chip
style, it is similar to a rip blade, but every other tooth has the
corners ground off and is ten thousandths higher than the rip teeth.
The theory is that the triple chip tooth does the hogging out, and the
rip tooth cleans up the kerf. I'm a big fan of them, personally.

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I'm familiar with TCG blades. Specifically, which Freud blade are you
describing?

The one I've got is a 60 tooth Freud industrial "Heavy-Duty
all-purpose" blade with a 10 degree hook. It's got an eighth inch
kerf, and while it doesn't leave a perfectly flat bottom, it's pretty
close. I don't have a saw with a long enough arbor for a dado stack
yet, so I use this one, and make several passes. The two tiny ledges
on either side of the cut come out very easily with a hand file or a
sharp chisel. I cut about 40 dadoes with the thing today (set of
bedside tables in maple and butternut, for the curious), and it worked
like a charm- no chip-out at all.
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