Okay, I don't know if anyone's been following the PBE change thread on the LoL forums, but a few pages into it, Xypherous makes some rather... interesting claims about hybrid items like Hextech Gunblade and Guinsoo's Rageblade...

"In my opinion, focused hybrid itemization is kind of a misstep, overall.
The advantages of having both AP and AD ratios is that any item is good for you - not that there's a specific class of items with 30% more stats because no one can use it correctly and thus it is good for you. When hybrid items are in vogue, like gunblade - it simply leads the detriment of any champion that can use it well.
The end result of that is that once you're balanced around hybrid itemization, you have 70% of the ratios of any other champion *and* you've effectively locked yourself out from any cool AD or AP itemization, defeating the point of being hybrid in the first place."

Now, I rather disagree with his trashing of hybrid items on the grounds of "you can build AD and AP items separately if you're a hybrid". To illustrate my point, let's look at one of the quintessential hybrid champs - Kayle, and consider how hybrid Kayle compares to pure AD/pure AP Kayle if there are no cool hybrid items to pick up.

(I am not an expert in building Kayle, so forgive me if I err.)

Hybrid Kayle picks up some boots, a Bloodthirster, Nashor's Tooth, Rylai's and a Black Cleaver for her offense. AD Kayle opts for boots, Bloodthirster, Infinity Edge, Black Cleaver and Phantom Dancer. AP Kayle goes for boots, Rylai's, Rabadon's, Nashor's Tooth and a Void Staff.

So... what's the problem? Well, hybrid Kayle only ends up with about 145 AP with no MPen, so her AP scalings and magic damage are now... rather rubbish, compared to our AP Kayle with 435 AP and a ton of MPen, with the same AS. Meanwhile, she's utterly outclassed in basic attack damage by our AD Kayle, who has slightly more AD, a ton of crit chance and extra crit damage from IE. So AP Kayle's chucking out more damage with her Q and E as well as providing some strong heals, while our AD Kayle utterly destroys people with basic attacks.

But what's this? Kayle has discovered some items that are actually designed for an AD/AP split! Suddenly, hybrid Kayle has a Gunblade and Guinsoo's to go with her Tooth and Cleaver! She now has a more respectable 215 AP with Guinsoo's stacked, a ton of spellvamp as well as some nice lifesteal, and more AS than even our AD Kayle! She still won't be outshining either of them in terms of autoattack power or AP alone, but suddenly she seems a much more viable contender.

And thus my problem with Xypherous' point is illustrated. Hybrids really need a couple of items to make up for the fact that they can't devote themselves to either their AD or their AP fully, or they fall into "jack of all trades, master of none" territory. Buy two AP items and two AD items, and you end up with both being a bit rubbish as your AP won't be great and you can't really capitalise on the AD you bought, and you don't have that much flexibility as you only have two items for each. But give hybrids a couple of items that shine on them particularly, and suddenly they're much more viable and can be more flexible in their choice of pure AD/AP items as you already have a respectable dose of both. And you still don't end up outshining the AP or AD counterparts in their respective fields, so it's not like the hybrid items suddenly become mandatory and you can't go one way or the other.

But that's just my thoughts on the matter. I'd be keen to hear what others think on it.