Yes I have replaced nearly every fixing on the bike with a Torx security bolt. Torx have advantages: They are less likely to be undone by a tea leaf; They are harder to 'head strip' than an Allen bolt; there is plenty of availability of different sizes; and they can be tightened to a greater torque than an Allen bolt.
Torx come in two flavours: High Security and Standard. The High Security bits have a pin in the centre of the socket. I went for the high security but in retrospect I think that this was a mistake, they are more expensive and harder to find.
Finally the best bit You should be able to get ALL major fixing (Ex the wheels) changed to Torx for less than £20 (including mudguards, rack, brake callipers, stem, handlebar, cages, seat post, saddle clamp, brake leavers, etc)
P.S. The only bolt I haven’t found in Torx is the pre load adjuster for the headset – if you find one of the right length let me know.