I have a decent amount. I have always been a DE defender, but I do get part of the complaining when I've had them near each other - the modes on JP, TFTC, Tommy and WWFRR are extremely similar. B/W games do "feel" different from one another. I LOVE the way that the DE machines are, but I don't like having all four of mine near each other or playing them close to one another.
That said, if you only have a few machines, they are the best bargain in pinball I think. JP remains one of my favorite games, especially lately