I tend to base most of my algorithms around direct logic - boolean algebraic structures - rather than continuous mathematics, i.e calculations. PIC's are not as well equipped for calculations.
Huh? Lookups have their place (and I love them when needed) but to say PICs are not equipped for calculations is just plain silly.

For all your projects (that you have posted), was time of the issue or code space? (answer = the latter). With your example equation, which one takes less code space? Which one is faster for larger I? (answer = calculation based approach).

Code:
' Calculation based equation A = 100/I +J*2
If I > 100 then
A = J<<1
ELSE
A = 100
FOR X = 1 to 100
A = A – I
IF A < I then OUT
NEXT X
OUT:
A = X+ J<<1
ENDIF
or
Code:
' lookup based equation A = 100/I +J*2
IF I = 1 then A = 100+J<<1
If I = 2 then A = 50 +J<<1
If I = 3 then A = 33+J<<1
If I = 4 then A = 25+J<<1
...
' (a bunch more  if-thens)
...
if I =100 then A = 1+J<<1
If I > 100 then A = J<<1