On the one hand, it seems like a great idea for churches to offer services in multiple languages. It enables them to say - rightly - that they have a diverse group of parishioners. But one negative effect I think it has is that it basically splits the congregation up into disparate groups.
If you break down the word "congregation" into its roots, it's supposed to refer to bringing people together. I think you do a better job of that with a single service.
I'm open-minded to what that *single service* would be. I think churches could be creative with the way they do this -- they could alternate from week-to-week with all-English, all-Spanish, all-Khmer masses, etc. Or they could mix up a single mass with elements of each. But I think the real key has to be one central weekly event (or the same event held at different times) that unites the group.