It depends on what you are viewing the footage. If you are watching the footage from a DVD on a 27″ TV, then I’d say you probably would not be able to see much difference, if any. If you are going to film, or upconverting to HD, then the anamorphic adapter is a must, as you need the highest possible resolution you can get.
The difference is apparent upon close inspection, but the decision to go with an adapter depends on your budget, the final destination of your footage, and whether the adapter will make a difference to you and your production.
On the other hand, I chose to not use an anamorphic adapter with my DVX, because of some aberrations the adapter causes. If I really need the adapter, a local guy will rent one to me. Otherwise I use the digital squeeze, and I’ve been happy with it.