After receiving my MA1e Kickstarter (although not the PDFs unfortunately) I can't see passing that beautiful hardcover around for use at the gaming table.
I also have the 25th Anniversary and 4e. My question is what mechanics changed between those three editions? I know the setting is different in the timeline, but are the rules different? Can I use my 25th as a pass around book while playing it 1e?
The 4e and 25th anniversary rules are different, but don't worry! For $15 you can get a print-on-demand copy of the original Metamorphosis Alpha rulebook. And the money actually goes to Jim Ward when you buy this version.
Also, if you check out WardCo on RPGNow, you can get PDFs both of the original rulebook, and of the adventure "House on the Hill" which contains both an adventure and random generators for using the Round House Modular Dwelling Unit. If you need an interesting MA location in a pinch, House on the Hill is great.