I've been using previous alpha clients -- ones with the old numbering scheme -- with few problems (or rather, no undocumented problems).
I downloaded this version, untarred it and tried to run it. I got the error message that it couldn't find the shared library "libexpat.so.1". So I did the following:
cd SecondLife_i686_1_12_0_51742/lib
ln -s /lib/libexpat.so.0 libexpat.so.1
and tried again... only this time it complained about not finding "libssl.so.0.9.8".
so I did this, again in the lib directory of the untarred second life directory:
ln -s /lib/libssl.so.0.9.8a libssl.so.0.9.8
tried running, and this time it was "libcrypto.so.0.9.8"... so:
ln -s /lib/libcrypto.so.0.9.8a libcrypto.so.0.9.8
and this time it ran ok. Whether this is a correct solution or whether it creates possible crashing problems with incompatible libs, I can't tell yet... but it seemed to run ok for the short time I tried it (ISP problems keeping me offline).