Okay I will write a bit about Develop.
When I first saw the card it seemed like a weaker cousin of Remake, an in a lot of ways it is. Remake is a card that can enable a fast ramp up of deck quality by rapidly disposing of the weak starting cards, and Develop can be played that way, but not to much effect. It is decent at converting Estates into Silvers, but for destroying Coppers it is strictly worse than Trade Route in lieu of some Highway/Bridge scheme.
And then of course it dawned on me that the real strength of Develop was the ability to set up a combo and place it on top of the deck. For this to be a viable strategy I like to see a good synergy between the $3 and $5 cards and, just as importantly, there must be a good $4 card that either pairs well with a $6 card of that you wouldn't mind seeing often. The board must be able to support Develop in another way as well: it must not be fast enough to make Develop obsolete, because this is not an ultra-fast strategy. I am thinking with anything as fast as BM/Masq may be too quick for most variations of this deck.
The key is the $4 card, for that is the card that wants to be developed first, gaining a $5 and $3 card that hopefully can do something strong together on the next turn. The $4 card should also be good enough to help progress the deck, because chances are that it may not collide with Develop right away.
The first $4 developed may be trashed for any $5 card and another develop, so a Gold can be gained the next turn. I really like to see IGG on a Develop board because it is a great target and immediately effects the opponents buildup. Or it can be developed into a nice $5 keeper card and a silver or a good cantrip. If there are $7 cards on the board, it may be a really good time to play Develop; I think it surely must be but I actually haven't played out that scenario yet so I cannot say for sure.
It is important to know that at some point this Develop chain must break in order to move into the VP buying stage; it is sometimes tempting to keep up the immediate gratification at a fatal cost to victory. With very few exceptions (like the KC/Masq pin), every Dominion deck should have as the main goal to progress the deck as quickly as possible to be able to gain as much VP as it can in the least amount of turns. Develop is no different. So if there are powerful $5 cards on the board, than perhaps using Develop to gain $5/Develop may not be the best strategy.
Develop is not easily put into a cubby hole, and I think that it is one of the cards in this set that will be creating new and interesting effects for quite a while. I really could not possible write a definitive piece on it because I have in no way mastered all the subtle interactions that Develop can facilitate. So to keep it simple: Use it on fours just about as often as possibles, and on fives if the deck needs a jolt of treasure or some other tricks can be seen. Absolutely ignore this card in very fast situations as it will not compete, at least as far as I have been able to discern. If there are very fast Develop strategies they are completely dependent on the cards available. Playing Develop on a board without $4 or $5 cards is complete lunacy, as far as I can tell. It is just asking for a beat down. Using it to trash Coppers should be viewed as a failure in most cases. And remember, the goal is to push the deck towards a winning end game, and other distractions may be fun and interesting but are ultimately kind of stupid.
Final edit