John Crichton said:
Aw, c'mon Darrin. I, for one, would love to hear your thoughts on this topic. 
* poke poke *
* prod prod *
Very well. I'll make a couple very general comments, and then after that, I'm keeping my silence.
First of all, I do very much respect Monte Cook's opinion. As his review points out, he was, after all, one of the three main people responsible for 3rd edition, which was such a huge leap forward from 2nd edition that everyone involved deserves a great deal of respect and praise. I also want to mention that I will be buying UA. Now, having said that, I have a few comments on a couple of his points.
First off, the stuff he said were good changes. I agree. Completely. All good changes, and relatively minor in terms of using old 3E stuff with 3.5.
Facing, I have no issues with one way or another. I didn't consider it broken to begin with. I don't consider it broken now. If I run into a situation where it is broken, I'll just use DM's fiat to make it more intuitive.
I think the only difference between squares and feet it that now a square on a battlemat represents a specific number of feet. But then again, it did before. No big deal there except that it forces you to think in a more linear and graphical way and makes it harder to game without minis and a battlemat. Any good DM can still make it work according to the old system. Again, IMHO, no big deal here.
Handedness is something that (I believe, possibly incorrectly) came about as the result of Savage Species. I don't know about the people on these boards, but there are definitely people using that book. Trust me on this! With character sizes varying now to a much greater degree than ever before, it helps to have a standardized set of rules on how to deal with weapons for size large and larger creatures. Yes, it called for a minor retooling of the old system, but I think when you actually get the book, you'll find the changes to be actually fairly minor.
I liked the NPCs in the old DMG slightly better. Open endedness on this particular table makes it less useful to me as a DM. Fortunately, I almost never used this table to begin with.
"The duration for ability score enhancing spells has been drastically shortened." This is what I would call a good change. You can still buff your character for a tough fight, but with the right combination of spells, you can no longer up your ability bonus for the entire day. This is a game balance issue that I think was properly addressed, but I can see Monte's point of view on this as well. I think the question is what you consider balanced, and that varies from designer to designer, DM to DM.
No problems with the new feats since most of them are reprints of feats that appeared in the splat books and simply
add to the number of feats included in the core books. Again, no big deal one way or another. I still think spring attack is broken.
His point about prestige classes incurring a penalty under 3.5 is valid. I don't know whether this was intentional or not and I don't know if it will be erratta'd. Personally, I would use the old system of not having them incur a penalty, for reasons I think anyone can figure out.
Overall I think Montes review is good and gives you a peek behind the curtain that actual WotC folk are not likely to provide. Now, enough reviewing the review. As for backwards compatibility, I slyly snuck the 3.5 rules into my 3.0 game without calling for a change in character classes, and I did it without any problems. In fact, that is how I would recommend making the transition. Use all the stuff from the combat chapter, feats, equipment, and spells chapters immediately. Most of that stuff is clarifications and in most cases will not change you game a whole lot. Switch to the reworking of the character classes when you start new characters.
3E D20 supplemental books work for anyone capable of critical thought and the power of deduction. Anyone familliar with both editions should be able the replace facing with space and intuitively deduce the proper number of squares the creature should use. 3rd party supplements and adventures work with little to no reworking of stats, and again these are changes that can easily be made on the fly. You shouldn't need to bother with the prep work before a game session. In most cases its a simple matter of a skill name changing, although only a few of these were renamed. Same story with spells. I have yet to come across any 3rd party rules accessory (not adventure or monster book) that requires any changing at all.
Finally, I think some of the additional material in the DMG is very useful. If only it would have been there when 3.0 was released. This includes the one thing I found most lacking back then - epic levels - advancement beyonf level 20. You should still get the Epic Level Handbook if you want to take advantage of all the cool stuff in that book, but if you just want to know the basics on how it works, it's here. In fact, I consider a lot of the Epic Level stuff a little over the top, so I would be willing to toss much of that and keep the general guidelines given in the new DMG.
Now I'm going to shut up. If anyone wants to look me up at Gen Con to discuss this further, I'll be available after hours.