I've been reading this thread for quite a while, and I'm beginning to think
that there are several options that aren't being considered.  Of course, it
could be that everyone considered them and decided they were useless, but
in any case, here we go:

To achieve a slow turn-on for a bulb, the best solution I can think of is
not, in fact a PIC.  It seems to me that what is needed is an analog
control circuit.  Something that regulates AC current the way that any FET
can be used to regulate DC current. (I don't know enough about TRIACs to be
able to say if they would be the answer) One possibility would be to use a
charging capacitor as one input of an analog multiplication circuit.  That
way the voltage could be slowly increased without the requirement of a
complicated digital control based circuit.

One way to simplify the idea would be to rectify to DC, then use MOSFETs as
current regulators.  Though the power consumption would be  a bit high, but
then it would be expected that that would be unusual.

I am having a similar problem at work at the moment, though the bulb life
has another factor that is not present in this discussion.  The situation
is that the light bulbs are having very short life spans.  Like 2
weeks.  They are the lighting for a shielding room for a permanent magnet
MRI.  Thus there is a very large magnetic field on them all the time, so
that when a current is passed through them, a force is created that
alternates direction 120 times a second.  In other words, being in that
room, causes the filaments to shake themselves apart.  When I was asked
about the problem, my answer to them was to rectify to DC, but no steps
have been taken on that count, so I'm not certain that it will make a very
big difference.

But I do think that using an analog circuit based on rectifying and
filtering the AC, then passing it through a MOSFET that is governed by a
charging capacitor is something that might work.  The details would need to
be hammered out, but it's still a possible solution.

As to voltage control, I was thinking that using a flyback switching
converter would be pretty easy to implement on a PIC, so if hte voltage
were too high, that could be dropped.

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