The USCCB has recently added a site to their main website which shows the changes that will take place when the new Roman Missal (in English) is implemented in the next few years. While many of the changes are subtle, they ultimately make the English more faithful to the Latin, and, in many cases, the Bible. I have heard praises and complaints on both sides of this issue, but I prefer to stay out of it for the most part. However, I do think having a more faithful rendering of the Latin original is a very good thing, even if it takes some time to get use to.
To see some of the most obvious changes, you can check them out here.
The date for full implementation has yet to be determined, but it looks like either Advent 2010 or 2011.
Another thing to consider is that very soon the USCCB will hopefully be completed with the NAB revision. This means that the Old Testament readings will be slightly different, plus the responsorial Psalm will be from the revised Grail Psalms.
So, lots of changes with the language in the Mass.