Even though the omens aren't good

Despite Philipp Petzschner (one of those Germans who I recently said were rubbish at tennis) winning the men's doubles, along with an Austrian who doesn't count for memory-championship-omen purposes, I've still got three days of holiday from work, which I'm going to spend preparing exhaustively for the UK Memory Championship in August, and we'll see how that goes. I've also pencilled into the schedule a certain amount of tidying up my flat, since my brother's coming to stay in a few weeks and there isn't currently room for two people to squeeze in among all the clutter. And I was also thinking of using this free time to work out what to do with my life, generally speaking. That doesn't take more than a couple of hours, I'm sure.

The project that interests me just at this moment is working out a nice balance between memorising and mental calculations to get a good score at the 'square roots of six-digit numbers' event at the Mental Calculation World Cup. What's the minimum amount of data (log tables or whatever) I can memorise that is still beyond what non-World-Memory-Champions can do and leaves a relatively simple amount of calculation?

Also, how can "I Can't Believe It's Not Butter" be advertising a new, more butter-like taste? Does that mean their whole brand name has been a lie until now? If it tastes more like butter now, that means it previously didn't taste entirely like butter, and so believing it's not butter would have been really quite easy! I mean, I eat the stuff myself and if they hadn't made it explicitly clear that it wasn't butter, I might have believed it was. But then, I'm stupid.