Which reamer?
 

Are some better than others and are the branded ones that cost over 10 better than the imports at 5?

ive seen some that have grub screws near the top of the cutting bit - is that for replacing the cutting bit?

cheers!

Yes its so you can remove the bit.

The only thing I have seen with reamers is make sure they are sharp!
if the end is blunt you will most likely cause more damage than good! (trust me I know!)

Its a tool, buy the best you can afford!! My old Dad always said where tools are concerned if you buy cheap you almost always buy twice.

Eds or Arrowmax

They may be exspensive but they last

Schumacher branded reamer is pretty good, and has a replaceable tip

+1 for EDS