Cna - I came on here when we first got our kittens in January asking the same question. Our cats have had no problem switching between wet foods. (Well, other than the fact that Spencer has selected the 6 varieties he will eat and CANNOT be persuaded to try anything else...)
If you're feeding any dry, though, you want to switch that over more gradually. I've noticed that it tends to bother Lily's stomach more if dry is abruptly switched. I have no experience on this with Spencer, since he refuses to switch brands of dry anyway.