MBB Consulting -> BB M&A - good/bad idea?

I'll take a crack at this. You should note that at the end of the day, IB is still an advisory role (as is consulting), so a lot of the same things you don't like may apply (you're not the one calling the shots). You are right that the end product is, however, more 'tangible' in the sense that a successful deal is one that closes and has some sort of material impact (hopefully for the better).

"- How technical and financial does M&A 'really' get? I'm using M&A here to include industry coverage as well. I would say I am solidly average at modelling and quantitative thinking in general. (and this is against the consulting standard which I imagine is lower than in banking). How much does success in banking require a natural talent and intuition for numbers?"

Not super technical, if you can handle consulting you'll be more than likely be ok in IB wrt to this. Your analyst will do most of the hard number crunching anyway.

"- Do investment banks get involved with post merger integration at all? Or does that belong primarily to consultants?"

Only if there's more fees involved. In other words, operationally, no; more transactions (be it bolt ons or selling the same company again down the road or some type of financing), yes.

"- I've heard from IBD analysts that MBA associates (particularly ex-consultants) are generally clueless. How true is this? And if so, what do you think gives them the bad rep?"

It's more so that analysts think everyone's clueless because they don't know enough to know that they don't know much of anything.To be fair though, new associates (in general, not just ex-consultants) do tend to be kind of clueless relative to an analyst who's got a year or two under his belt.

"- In the medium term, if my goal is to join the Corporate Development (Internal M&A) team of a F500 type of a company, would y'all recommend a stint in IBD? Or does the MBB stuff provide enough of a foundation?"

Not my career path, so I'm not sure, but if you're already set on MBA, why don't you try to get into F500 Corp Dev out of school, with a back up in IB?

"- In the super long term, have you seen much success in senior M&A leaders entering the C-suite - either as a CFO or even CEO?"

Again, not the best source on this but my general sense is no. Bankers are deal guys. They aren't operationally involved enough and don't think on a long enough timeframe. Like you said, being a senior banker is about being a salesman first and a manager second, and I feel like most companies would rather have those flipped for a CEO. I think most of the BB's don't even have M&A guys in charge (although I suspect that's more because most of the revenue for these banks tends to come out of the S&T side).