Got my multi in a Duchess but that is the only time I have in one. From what I have heard and experienced, it depends on how you look at it. As a trainee, it is nice because it has counter-rotating props so there isn't really much of a critical engine and the rental rates are usually as close to affordable as you will find. However, don't let this cause you to get lazy and complacent when you move on to other planes. The single engine characteristics of planes with larger engines that don't have counter-rotating props, such as a Cessna 310 or baron, will be quite different and more challenging that the docile Duchess.
I got my multi rating in a BE-76. Its a great airplane to start in. I hope you like it. If you want any hints or tips email me and I'd be glad to help in any way possible. /ubbthreads/images/icons/smile.gif email@example.com
I have some time in the BE-76. It was harmless. Nice, logical panel, and good visibility. Doors on both sides. It has unfeathering accumulators, whereas the older Seminoles don't (this will become important to you later on).
All in all, a nice, tame aircraft. Like any piston multi though, single engine climb performance is about nil (or worse) if you are on the fat side of the high/hot/heavy equation.