Any more details?  Is it plug and play?  Do all the timing components from the M42 work or do you need to use M44 gears?
Any first hand experience is appreciated.
I put an M44 head on an E30 M42 block.
There are a few things to remember.
They are interchangeable, but as indicated the series 2 M42 heads and M44 heads used a 4 wire single sensor for temp.  This does not work with the E30 gauge cluster.
The timing components are the same and interchangeable, but if you use M44 timing covers the cam positon sensors are in different places.  You may need to "reset" the cam position so that the computer still gets the right signals.
If your using a series 1 inlet (E30) with the "log" manifold, you cant use the rockercover, it hits the inlet.  If you change over to the "curvy" series 2 or M44 manifolds, no problems.  
Also the M44 rockercover has oil squirters in it to lub the roller rockers.  I changed all the gear into the early rockercover.
After a little work the M44 head will fit.
I've now done over 20,000 km since I did my head change and have had no problems with it or the top end of the engine except for not having an accurate temp sensor on the dash.
Cristian