I just did an ECV in mid-August. I was really nervous about it because I'd never rented one before, but it was great! Everyone was so accommodating and I didn't have a single problem. Well, other than a teenage boy who for some reason know only to him, decided to walk BACKWARDS on the walkway in Adventureland and ran into me!
The rides kind of vary but it's very easy to deal with. Many of the rides have separate handicapped entrances that are clearly marked. You just approach the CM there and they will explain what to do. If they're not marked, you just go to the CM and ask. Most of the DCA rides you can just take the ECV through the line. But many of the DL ones are at the ride exits. IMO the one that was the most difficult to deal with was Splash. The handicapped entrance is clearly marked and is near the exit, but to use it you have to go in the Splash exit, which often is filled with people going pretty fast around corners trying to get back in line and it's hard to see around those corners. Then once you get to the room where the ride photos are, that's really crowded and can be difficult to maneuver. But keep going and you'll eventually get to where the ride lets off. You park the ECV there and board from the exit side. I'd recommend if you do Splash, have the people who are not in an ECV go first to clear a path around those corners. Although I did it once by myself and it was fine.
Keep in mind that you won't be able to get directly on rides such as Splash with an ECV unless you have a fastpass and your time has come. Otherwise, they'll tell you a time to return that matches up with the current wait time.
The view for F! is great from an ECV. The person in the ECV will be sitting up higher than everyone else because everyone in that section is required to sit. You can definitely take 6 family members. They will be able to sit in the same area. You do need to get to the FP return area about an hour before F! starts, where they'll direct you to a special handicapped waiting area. I'd recommend being towards the front of that area if you can because the people who go in first will have a more centered view. The ones who go in last will be towards the right, more in front of River Belle Terrace.
DO get a 3 wheel ECV if at all possible. They are smaller and much easier to maneuver than the 4 wheel ones. One CM told me they're always glad when a 3 wheel comes through the line because they're so much easier to deal with. I rented mine from Deckert and it was great.