I have not had one of the electronic reversing units fail from Lionel although another member in our club did suffer a failure.
Now if you never think that you might go to Legacy or TMCC buying the Dallee may well be your solution, but if you may be looking to go to wireless control I would consider the Cruise Lite from Electric Railroad. It will operate as a reversing unit on a conventional layout. If you later decide Legacy is something you want to do you would not need to pay again to convert this engine. I have put these Cruise Lites in several PAs and am very much an advocate of the Legacy system. The Cruise lite will be more expensive (price about $85.00) but down the road may save you some money.
Ray