I bought Medieval Madness when it stopped being table of the month. At the time, there was no choice to but a "pro" version, but I noticed that it had all the pro features. I thought I was pretty cheap that it auto converted to the non pro version on the next update. Admittedly I didn't know what I was buying, but the table presented to me at the time I purchased it was not the table I ended up with after the next update.
Also, I have to say that the operators menu and the ball control are probably enough to get most people to buy the pro version. The inability to explore the table without paying the extra fee really detracts, especially when trying to learn the game. When these games were in the arcade, we could explore the play field all we wanted for free. It doesn't seem like being able to read the text on the play field should be a premium option.
Other than the above, I think it's a great game. You should just be a little more up front about what is actually being purchased.
Also, I have to say that the operators menu and the ball control are probably enough to get most people to buy the pro version. The inability to explore the table without paying the extra fee really detracts, especially when trying to learn the game. When these games were in the arcade, we could explore the play field all we wanted for free. It doesn't seem like being able to read the text on the play field should be a premium option.
Other than the above, I think it's a great game. You should just be a little more up front about what is actually being purchased.