Homebrew PCBs

Following the recent posts on BGAs, I'm curious what people consider the 
lower size limit for SMD to when doing home brew PCBs and projects. I 
used to use 0805 but found soldering 0603 parts wasn't that much more 
difficult, and so its my preferred choice for a new project. I 
experimenting with some 0402 on scrap motherboards and found it way to 
tedious to be practical. A big problem I see with 0402 is an inability 
to run a trace between pads.

I found the no-lead chip scale packages (QFN) are somewhat more 
difficult to solder than corresponding leaded TQFP of the same pin 
pitch. Without reflow soldering, the pins of a QFN rely in wicking of 
solder applied from soldering iron tip located on the pad just external 
to the package. Its difficult to know if solder as wicked between pad 
and pin.