I voted 526-545, which seems like just enough to make a very good, OU worthy pokemon. I'm also going to vote medium in regards to speed, although I'm hoping more specifically for the higher spectrum of medium like 80 or 85, because I think too low would leave too many stat points for other stats, and considering speed can be cured by Sunny Day, that might lead to it being a little overpowered. I think offense should definitely be emphasized over defense, because the type really does not lend itself much to defense. It has like 3 resistances, one of which is to steel, and a Stealth Rock weakness. The typing does give a few very good matchups, most notably I would say against Celebi and pretty much all electrics, but overall most of its defensive matchups come out to be pretty neutral, which is why I think this pokemon would be better off as a bulky attacker, rather than a somewhat offensive defender.
I'm still not exactly sure what I would like this pokemon to look like, but right now I'm thinking something along the lines of 70 / 90 / 80 / 110 / 100 / 80 (speed last), which brings it to a solid 535. That spread gives it bulky enough defenses to take a decent amount of hits and allow it to be a sort of a soft counter to a few specific threats, enough Special attack to be a very serious threat under the sun, enough attack that it can attempt to threaten Special walls with a double STAB physical Fire move I guess (kind of like raindance LO kingdra's waterfall), but not really enough attack to make full on mixed sweeping really viable. The speed I'm not too sure on, because we still don't know if it will have Chlorophyll or not, but 80 seems like a decent number, allowing it to outspeed slow stuff normally, and pretty much everything but Deoxys and Scarfgar in the sun if it gets chlorophyll
Ok so after looking at it, that seems a maybe a tiny bit too good, but then again this is a Stealth Rock weak pokemon with only two or three resistances (Grass, Electric, Steel, am I missing one?). Anyway, I'm not attempting to submit a set or anything, I'm just weighing in on the matter to hopefully give some people ideas.
Edit: Eh, after looking over most of the spreads presented so far, it looks like this pokemon is going to be alot like exeggutor, just alot better :/