Both 0.3 and 0.5 versions run slow for me with Indy4, Dott and Sam`n`Max, unless I switch off the sound and music (which didn`t work in 0.3 for me).
So version 0.5 is better because I also wasn`t able to make savegames in 0.3 with Monkey Island 1.
Oh, and playing with sound and music, in version 0.3 the music makes a crackling noise, but in version 0.5 it doesn`t.
So for me version 0.5 is the best! But I hope there will be an update soon, that changes the cursor speed. They could make that by pushing the R button the curser gets faster or something like that.
I recommend you to stay with 0.5, but if you like to try out
here is version 0.3.