I was going to wait until I had completed Tactics Modules 1-3 before doing the review, but after completing a little over half of Module 1 I think that I have enough information to do it justice. I can confidently say that Personal Chess Trainer 2007 (a.k.a. PCT 3.0) has a fairly substantial number of corrections, revisions, updates, and extensions to the problem set presented in PCT 2.0 as well as some completely new problems.
To expand a bit on that, I have run across a few problems so far in Module 1 that used to be in Module 2, meaning that they have re-arranged the problem set in some places. I'm assuming that this is to improve upon the progression of difficulty. There have been a few revisions and updates where problems have been changed (slightly in some cases, more drastically in others.) There have been extensions...for example there was a problem that used to be a two-mover in PCT 2.0 that ended one move before mate (the mating move is largely obvious) that has now been extended to include the mating move. Finally, I have run into problems that start the same as those in PCT 2.0, but follow up with a different reply from the opponent. In one case (problem 389) it was changed from a mate-in-three in PCT 2.0 to a mate-in-six here...same problem, but more difficult reply/variation. UPDATE
-- After finishing Module 1, I can add that (perhaps best of all) it seems that the few problems that I was never able to completely "understand" or that just didn't seem to make sense (even after studying them extensively with Fritz, variations and all) have been revised to make them and their associated solutions much more clear and less ambiguous.
In addition to the changes to the problems and problem sets, the interface has been fairly heavily updated. It's a nice looking change in my opinion. Probably the two largest functional differences are the integration of the crafty engine and the ability to traverse back through the problems that have already been completed. Previously, once a problem was finished, you could not back up to it without re-doing the unit. A very nice update...
Finally, two new sets of Modules have been added: Openings and Commented Endgames. The Openings Modules seem somewhat offbeat, offering King's Gambit, Queen's Gambit, English Opening, and Larsen's Opening. The Commented Endgames include modules on Elementary Checkmates, Pawns, Minor Pieces, Rook, and Pieces vs. Pieces.
All-in-all, it seems to me that Personal Chess Trainer 3.0 is a worthwhile upgrade for owners of previous versions and highly recommended for those who've never tried it. At the very least, run over to the PCT website
and give the free trial version a go.