As a former CM, I can say that it is a problem. I have run into many people who rent them and then yell at me when they do not get front of line access on many rides because the rides can accommodate them through the normal line. Sadly, there are more people than we would like to admit who rent them thinking they won't have to wait in line ever. That is not the case anymore. These are the people that I despised dealing with because they became downright abusive to the CM's.
Now, this was a small but vocal minority. The vast majority of people were very understanding. Sometimes they would leave the
ECV outside the ride and walk the line because a transfer to a wheelchair was required. On rides with elevated load platforms like Winnie the Pooh pushing the wheelchair up the line can be very difficult, so it was easier for them and their family to walk. This does not necessarily mean that the person did not need it. Most people who rent have enough stamina that they can stand in the line, but an entire day of walking is too much.
I have been run over by several ECV's, and had my achilles tendon damaged by one. The biggest gripe that CM's have is that many people do not know how to drive them and turn the speed up to fast. We have sent many people to first aid because somebody did not know how to drive their ECV.
There are several things that WDW can do to alleviate the problems with the ECV's while still having them available for those that need them:
1.)
Teach people how to drive them. Have them do little course around the rental place to show that they know how to drive it before turning them loose in the parks.
2.) Widen walkways so that there is enough room for the ECV's and pedestrians. They also need to paint the curb on mainstreet a different color because in the dark you cannot see where the curb ends and the sidewalk begins. I have seen several people go off that curb at night.
The ECV's are a great aid for those that truly need it, and really, the vast majority of people are responsible and kind. Sadly, it's the vocal few who ruin it for everybody else.