The Puzzleknots are two mana artifacts that have a minor effect when they enter the battlefield, and can subsequently be sacrificed to repeat that effect at an additional colored mana cost. Let's take a closer look at the cycle:
We won't really get a sense for how good Glassblower and Woodweaver are until we have a clearer picture of what you can do with energy counters at Common. Getting to Scry 2 for 2 with the Glassblower is probably the best deal in the cycle, and if energy counters prove useful, then this will probably be the best of the five. And while generally Lifegain cards aren't great, it's surprising how effective an additional six points of Life can be in a close game, even if you are paying 4G for it.
I've always loved the design of the Spellbombs from Mirrodin and Scars of Mirrodin, but it remains to be seen whether these will end up good enough to live up to that comparison.