Well....it worked, but it showed me that I didn't read the mod list as closely as I thought. The list of items that are in dw20 that are NOT in infinity can be found at
http://pastebin.com/X5khqET7
Anything from that list will be deleted from your world. The biggest kicker for me was the loss of powersuits. Yeah, it's totally OP by any standard, but it's pretty fun
Losing thaumic exploration was also a pretty big bummer.
Not having every square foot of dirt covered in pneumaticraft plants is kind of cool though.
So yes, it transitioning from one to the other works fine, you just have to be prepared to lose a lot of items if you use certain mods like powersuits, factorization, thaumic exploration, and pneumaticraft.
I still might consider doing it, since it adds some good stuff too, and will likely be updated again sometime in the future. You also have the option to add the mods back, but that takes away the ease of use for clients joining your server.