The alpha dial is worse than sliders, yes. I wish I had the full slider programmer for this thing. But it's not terrible. Much better than programming a Yamaha DX series synth with the membrane keyboard buttons.
I think MIDI-Quest for the Amiga allows one to program an Alpha-Juno. Otherwise there are a bunch of free editors for the Alpha Junos for other platforms.
I have the MKS-50 (rack version of Alpha Juno 2) and there's a driver available for use with MSE (Midi System Explorer). It should probably work straight away as they use they use the same sysex.
It's actually fairly easy to write your own driver as long as you have the midi/sysex information for the synth
