Here's what Cook's Illistrated says about electric knives:
RATING ELECTRIC KNIVES
"Electric knives might seem like relics from the 1960s, but we wanted to see if these knives had any place in the modern kitchen. We selected four new models under $20 and tested them slicing roast beef, turkey breast, angel food cake, and apple pie. The results were clear: Contrary to manufacturer claims, electric knives are not adept at slicing meat neatly and thinly-all four models shredded beef roast. Plus, they're aggrevatingly loud; we prefer to carve with our favorite slicing knife. What their powered pairs of independently moving serrated blades do best is is cut through delicate baked goods without crumbling and slice through crisp turkey skin without ripping." - Merideth Butcher
Here is what they recommended with reservations:
Oster
Rrice: $19.99
Blade Length: 7 inches
Turkey Slicing: 2 out of 3 stars
Roast Carving: 1 out of 3 stars
Dessert Slicing: 2 out of 3 stars
Design: 2 out of 3 stars
The other 2 models that got the same rating were across the board were:
Toastmaster at $10.79
Elite Cuisine 2 Speed Electric Knife at $16.99
Not Recommended was the Black and Decker Slice Right (which I own only because some one gave it to me) at $16.95
I've used my Black and Decker for slicing just about every thing with out much of an issue. I agree that it does better slicing breads than it does meats. But, when I slice meats, I usually slice what we're going to consume for dinner with my chef's knife. I then wrap it and stick it in the fridge over night, then put it in the freezer for an hour or so before I slice it with the electric knife for sandwhiches and what not. Maybe this is why my slices don't tear?