We've used MySQL for some intense projects in the past. The problems that we encountered tended not to be with MySQL itself. I had queries that choked in the application but would run fine in SQLyog. It was the .NET connectors. I one failed project (yes, I've had them too) while the database performance was an issue it was not the killer.

I also have been fearful of the takeover. At first I thought about the the "buy it to kill it" thing. More likely it will be the "let's merge all the teams so that we can look like we are saving money" thing. It's a slow poison. All the stuff that people hate about A (and the reason they didn't but it) will bleed into B. When B dies a slow death then the hymn sung over the grave would sound like "We were right with the first product all along." We have all seen this before.

No as to one entity owning two some what competing products. I don't see that much of an issue. Case in point is Microsoft owning Apple. In the car wars Buick competed with Oldsmobile. Mercury competes with Ford.