Have to admit, I know very little about this line from Infinity..but they are all well respected everywhere from what I see.
Over on AudioKarma the consensus seems to be that the tweeters should be replaced due to ferrofluid loss, and that they are fragile as TLS Guy has stated.
Some owners find the 40's sounding dull and prefer the 10's, with some considering the 10's the star of the line.
That's the one! honestly you get use to how muffled and dull the tweeter is in the Il 40's if I listen to my Epsilon for five minutes and switch to the Il 40 it's a joke, honestly when you first install the new caps you will think you wasted your money like I did but once they break in you won't...
audiokarma.org
Personally if I had a pair, I would pop that gray plastic panel off and paint it black...looks cheesy to me.
And, as always the OP won't know if he likes them until he has them.