We used the charted buses as well, and I think they were some of the best money we spent. Especially since it poured on our dessert party! It was much easier for our guests to get to the buses that were waiting backstage for them rather than have to worry about getting to the front of the park in the rain. In addition, it was nice for our guests not to have to worry about using Disney transportation (which can cause them to run late) or finding their own way to the various venues (disney roads can be hard to navigate if you haven't been there before). My DH and I used the Vintage Rolls to get to the ceremony (we saw each other beforehand for pictures) and the reception, and then boarded the buses with the rest of our guests for the dessert party.
As far as using Disney transportation to get you to your wedding - while it is a fun idea, I imagine that your EM (or whatever they are called now) will discourage you from that. Depending on where your wedding is (for example disney transportation won't take you to the WP, and its about a 5 minute walk there from the GF) and where you are getting dressed (there is no resort to resort transportation), it could be a big hassel making sure you get to your wedding on time. Its worth asking your EM about, as I agree it would be really fun, but it could also end up being a big problem the day of the wedding. But, there have been brides who have used the monorail to get from their ceremony at the WP to the Califonia Grill for their reception.