UC520 with 1861 code?

has anyone tired to load the OS for the 1861 on a uc520?

If so what are your experiences?
If not does anyone know or think its possible?

I started with CME when it first came out and never really understood the major differences between the UC500 and the ISR. Now that Cisco has release the 1861 the waters are even muddier! I guess from a marketing perspective Cisco wants to push into the SMB, but they are not very clear as to "why" you would pick one over the other.

It seems to me that