I'd say checking would not be a problem (I've done this, but without spiked feet) as the idea is that you don't have a weapon handy.

However, I haven't tried to carry-on my tripod - spikes or not, most tripods would make a nice club, and I'm sure you could conceal things in the legs or otherwise transform it into an instrument of mayhem.

Why don't you try emailing the TSA yourself? They've got their own website: