I was a softball player and it was an interesting transition. I have a tough time bowling cause you can't bend your elbow...you have to throw it straight. And if you are used to pitching with a bent arm, it's a hard transition. Hitting is also different - you hold the bat differently, the ball comes at you differently (hits the ground, may spin, may go at 90 miles per hour in international games)...it's similar but very difficult. I think pro baseball players would struggle a bit at first due to all the small but important differences. And no - it's not easy to hit sixes. And the block isn't really like a bunt...and the reason for the block depends on a lot of things.
Another thing to think about is that their is a huge amount of strategizing while hitting - you may be the first batter and need to just stay in there as long as you can during a test match...you want to wear down the best batters...so you won't go for huge hits. The guys in the middle (3-6) may be the biggest hitters though even they have to think about how they're going to hit and where. It's a mind boggling game once you get to the 'big leagues'!
Matt...where do you live? If you are in London, keep an eye out on this board next spring as I'll invite people to come watch a game...we'll go to a club team game (quite competitive) and then if people like that I'll see if we can get tickets for Lords. If you aren't in London, then I'd suggest finding a cricket league near you to watch...it's cool!