Imbue is definitely going to change item value. My expectation is that ueber items that you can imbue will suffer a dramatic loss in value, in particular those 20M bracelets with 25DI, 13DCI, 10HCI and +10 Ninjitsu. I would recommend that you sell that stuff now. Anything I am not currently using that I think will be devalued with imbue has been going on my vendors at discount prices. As I think about it I am going to drop a taming/lore Mark of Trav on my vendor now.
There will definitely be things that you can't make with imbue that hold their value as imbue limits the higher end of certain characteristics. Rune Beetle Carapace will still be something you can't make an equivalent, although you should be able to do something that would be a solid alternative. Swords of Prosperity is another example. Orny and AoF are others.
All in all I don't mind the change even if it devalues some of my stuff. The game is item based now, but there is a huge inequity in it between the have's and have nots. If you have 100M to spend on a suit you can generally PvP with a great deal of success against someone with more skill but no gold to spend. Imbue will level the playing field and make the game more skill based again by making the top tier stuff widely available. It might cost 20M for a suit, but that is a reasonable target for a MUCH bigger percentage of the population than what it takes now. It will also mean A) that crafters will have a pretty huge relevance again as the best items will be crafted and B) make champ and peerless spawns a bigger deal because a lot of the ingredients come from them.
In balance all of that seems positive to me.