I noticed that v1.5 seemed to take a very long time to load.
By "Load" I mean the time from clicking on the startup icon to where my Inbox messages are shown. Both versions are on the same USB stick.
v1.0.7 took 16 seconds
v1.5 (20051025) took 2 minutes and 51 seconds.
Both versions had about the same number of messages in the various folders.
Both have compacted folders.
Plus, I see in v1.5 even though I have set check for new mail every 20 minutes, nothing new is ever in my Inbox until I manually click on Get All Messages.