here is one i knocked up a while ago using the lm2575 ist attempt (reg1), worked really well just followed the data sheet which recommends every track to be as short as possible i then surrounded it with a gnd plain, everything on the board worked.
noise was an obvious concern so i knocked up another 2 identical circuits (lm2575's) then placed them on top of the processor still everything worked as it should. i have experienced very noisy environments ie equipment that effect the operation of processors you can see straight away as it up sets the functionality of it also another good way to see noise is to monitor serial data from the processor noise really does upset the data.
i then used this board to see if it interferes with other equipment such as mobile phones and even placed on top of a i7 processor under load and didnt effect the operation of it i couldnt get that circuit to effect anything, my version of emc testing 
so it can be done, building stuff you learn so much from it.
