Check out the trial of 6.01. In all likelihood, the UI will not change that much. If you can swing working in 6.01 then most likely you will get along fine with v7. For example, the 3DS MAX UI has not really changed since v1 ... not all that much ... and we are now on ... what? ... v9? Photoshop's UI has basically remained pretty much the same ... it looks better now and is a bit better organized, but it is still basically the same. Most 3D apps are not going to drastically change their UI unless there is a drastic flaw in them. And even then they may not. To change their UI drastically would cause them to alienate the people who have become familiar with the software and use it on a daily basis.

So get the v6 demo and give it a try.