Sticking to what i said at the time he was announced as a Merc driver, that he is probably the closest match to Nico as Merc were ever going to get. I expect him to be quick in quali, able to lead from the front and to be found wanting a little in wheel to wheel combat.
Basing this on what I've seen of him so far in F1. In quali, he seemed to have a decent edge over Massa. If you're going to be challenging Lewis, its something you would expect. Can see him causing Lewis problems here if he does a better job setting the car up, or Lewis has an off day.
WRT his racing skills, what i always seemed to observe with Bottas was that, for the most part, he was clean, but pretty passive when defending. I was always pretty critical of him for allowing himself to be overtaken so easily. However, like Nico, when he did decide to get his elbows out, he made an arse of it. Think Kimi in Mexico.
It'll be tough for him, no doubt, coming into a new team is never easy and people shouldn't be too quick to write him off if he struggles early on, but i think he'll do fine.
Lewis is Lewis, no concerns there, he'll drive the arse off it and if we really do have a 3 team battle, then this is where he will really shine. Bring it on!