I've got the Welbilt R2D2 style machine, which I'm quite happy with.
To slice tall loaves of bread, I usually use a steak knife to slice
the bread in half horizontally.  Then I slice each half into parallel
vertical slices.  This makes for long thin slices that look a bit odd
but are easy to use for sandwiches and toast.
The most recent DAK catalog has a gadget to use to cut a loaf into
evenly parallel circles.  It's about $30 and comes with a flour sifter.
-Valerie Mates
popcorn@cyberspace.org  -or-  popcorn@grex.ann-arbor.mi.us