I've moved from MS to BC. Mostly without difficulty. And it gets better all the time with the tips on the Zumo Forum.
I am currently using a Zumo 550, which I'm very happy with.
One of the things which has been missing from both MS and now BC, that I use for almost all of my route planning, are County Borders, and County Names.
I, and many other people, do the Harley Owners Group, ABC's of Touring contest each year. The idea is that you get photos showing your Harley, a specific category of sign, and a copy of a HOG magazine, to prove the correct year.
One of the categories for points in the ABC's is Counties.
I've attached one of this year's ABC's County photos (Queen Anne's County, MD) showing what I mean.
Since neither MS or BC show counties, I find myself always creating duplicate routes in Street Atlas, by DeLorme. (I believe Microsoft Streets and Trips also does this) And even SA does not include the County Names, they just show the borders.
But apparently there is also a HAM Radio contest whereby HAM operators keep track of the Counties of other HAM operators they have contacted. And one very nice gentleman took the time to create a file of every County name in the US, that can be used with Street Atlas, so that the County Names appear on your SA map.
In any case, I would very much like to be able to see County borders and County Names on my BC maps. And as a plus, be able to control the size and color of the names, which you can do with SA.
Thanks for your consideration,
Don Sepanski