You can now order a modified Panasonic G1 or GH1 so that the IR blocking filter has been replaced by a clear filter which will allow better hand held infrared photography and much better nebula astrophotography.
The momentum for Micro Four Thirds is escalating, although it would be nice if Panasonic or Olympus added live video output feed and improved remote camera control in future models to make them even more useful for astrophotography.
Hutech will modify your camera for $US500 or you can purchase a modified camera from them.
To shoot IR, you can just purchase an IR filter for the lens.
To shoot daylight, you will need the daylight filter and do a custom white balance.
If you do not want to use IR filters on the lens, and you wish to shoot IR, then replace the IR blocking filter with a 715nm filter – but you may also need to remove the dust-shaker glass (thus disabling dust protection) as it seems this also blocks IR, at least on the Panasonic cameras.
ps.. another conversion service in the USA (Precision) is discussed here
Here is an example of a hand held photo by Carl Schofield from a Precision IR-converted G1 using a 715nm conversion filter with 14-45mm kit lens at f/8, 1/320th sec (click for larger size):