Here are my comments right now:
1) why are you playing painter/grindstone in this deck? If only for the random colorless "I win" factor why is this not leyline/helm?
2) why are you playing 4 grindstones? It does nothing on it's own and 2 are redundant, come to think of it...so is painter in this deck, but at least it's a creature.
3) why aren't you playing any cards that benefit from a painter in play other than grindstone? what color do you plan to name? There are many ways to approach this, black for cards like reap and compost, blue for cards like red blast red for some of the white hate and blue blast. In general people go with blue because red blast doesn't suck without painter.
4) null rod is incompatible with your win conditions and one or the other should be removed. If you're planning to win by activating an artifact null rod is a PROBLEM for your deck. If you like null rod you need to find another win condition.
5) you're playing 19 mana sources and no real draw engine. 3 meditate and 1 top does not a draw engine make. Have you considered Bazaar? Moxes and lotus come to mind.
6) your disruption suite appears to be insufficient to support meditate. if your opening hand is disruptive enough that you can cast meditate, you won't need to meditate, if your opening disruption is insufficient meditate is unlikely to provide enough protection to get you through your opponent's turn.
That's what I've got for now, I'm sure other people will have other comments.
1 I like the combo, in fact I love it, I'll sideboard in the Leyline if you're running Gaea's blessing
2 Ever heard of Jester's Cap it takes 3 cards, it's happened to me before, 4 copies is correct, you are not thinking about all the possibilities that disable the combo.
3 I'm calling green work with that and find out that it wont help or hurt me
4 Null rod is sweet, and I'll surprise you when I destroy it with a Sol Ring, Mana Crypt, and Mana Vault on the table to be used to combo off.
5 Bazaar is a good idea, I like it, but I would have to utilize the graveyard a little more to warrant that.
6 You only meditate when your hand is burnt, it's not for opening hand use