The big reason, of course, to make sure that the model geometry you're working with is the same as the authority model. But that's true for all CAD users -- not just SolidWorks users.
For SolidWorks users, model reuse in downstream processes is becoming more common over time. Either people send you models ("Here, use this"), or you send them models. If they don't have the exact same version of software that you have, you can get in trouble all too easily.
Over the long term, you're probably going to start getting models from, or sending models to, people using the new SolidWorks V6 products. If the programmers at SolidWorks get everything right, the transfer of data between these systems will be flawless. But history says... you're asking for trouble if you can't verify this.
This Thursday, Nov. 8, at 2:00 pm ET / 11:00 am PT , I’m hosting a free webinar with Capvidia, to talk about data verification in SolidWorks.
Capvidia is going to be talking about how their CompareWorks program can diagnose the geometry you import into SolidWorks and show where there are differences and/or give you the assurance it is correct. And how you can use it to establish a documented, traceable procedure in your company workflow. (CompareWorks is a Gold partner product, and works seamlessly inside of SolidWorks.)
If you’re a SolidWorks user, and you work with imported geometry, or you’re concerned about how to handle compatibility between your existing version of SolidWorks and the upcoming SolidWorks V6 generation, I think you’ll find this webinar to be really interesting.
I actually asked Capvidia to do this webinar with me, because I think the subject is important.