I am really tempted to return mine (I haven't used it yet) and exchange for the 665. But, dang I got such a good deal on the 615A that I am not sure it is worth it to switch or not.
After my latest use of my new 615A, I'm rather disappointed and would encourage an upgrade if that is still an option for you. When I sliced the bacon I had no problem at all. Last Saturday I decided to smoke some cheese. I used the slicer to slice into all four sides of 4 blocks of cheese on its deepest setting so that it would be easy to use a knife to finish the cut and have uniform chunk sizes for smoking.
The 615A couldn't slice very deep into the cheese block because it would very quickly hit the blade housing. It would also every so slightly bog down the slicer when I was cutting the wider size of the block. And then it actually blew the fuse on the slicer on one of the cuts. It was pretty disappointing. I don't dislike the slicer entirely, but it seems a little weak on the power side and I'm not encouraged by the idea that I'm going to have to buy and keep a bunch of fuses on-hand for any time it even minimally bogs down. I really wasn't working it hard so it seems like it should have handled it better than it did.