I have an older hardware machine and I’m running 1.23 (Sep 30 2014 here), which includes incremental sample uploading. I have thought about upgrading to 1.25, but I approach updates really cautiously with this synth. Things are working well right now and I haven’t seen much beyond fixes for the new hardware they put in the synth, so I’m not going to mess with it.
BTW, it does require a new version of spectre (1.0). I was able to verify my version on macosx by going to the folder containing the app, ctrl click, get info.
It uses checksums to keep track of what samples have been uploaded, so if I remember right, the first time you use the new version, you might not see the benefit. But the second time you should.