How do I feel about multiples of the same mold?
Well, my collection mainly focuses on "Classics" style toys, and in that collection I collect characters, not molds. So if two (or more) characters happen to share a mold, then as long as the mold makes sense for both characters, then sure!
Examples include both characters who also happened to share a mold in the G1 days:






(I know I have one somewhere, but I can't right now find a decent pic of them together with Magnus armored up. But I figured it was unnecessary here anyway, since the point was to highlight that they used the same mold.)
And characters with "Classics" style toys that the designers planned ahead and made a mold that could effectively pull off two (or more) different characters with the help of some retooling and/or an alteration to the transformation scheme:




Somehow I haven't photographed them together outside of larger group shots, but the recent Springer and Sandstorm would fall into this category as well.
While I don't go in for troop building much, Scourge
did need at least a pair of Sweeps:


And... well... the one time I delved into the dark world of knock offs, it was for more uses of the seeker mold:


And, of course, Wreck-Gar needed a hog:

And delving outside of Classics... I also collect Optimus Primes. And let us take, for example, the original G1 mold. I didn't feel a need to get the original G2 Optimus Prime, since he was basically just G1 Prime with his trailer colored black and a few extra accessories tossed in.
But there was one other variant I
did have to have, as he was too fun to pass up:

He does have a very unique trailer, of course:

...that you can have fun stacking all sorts of stuff in!


In short, there are a
lot of toys in my collection that I would not have if I looked at it and said, "Nope, already have that mold." Why would I only want to choose one between Wheeljack and Tracks? Or only one of the six (main) seekers? There would be a lot of great toys that I
wouldn't have!
Of course, that all being said, as I said way back in the beginning, the mold has to
make sense for the character! For example, even if I didn't already have two great Warpaths:

I wouldn't feel any great desire to pick up this guy when he comes out:

And in this case, it wouldn't even be a duplicate mold, since I never picked it up as Megatron! (Not to say it was a bad Megatron, I just didn't need another Legends Class Megatron.) But that mold just does not say "Warpath" to me, even when they stick Warpath's head on it.