XPLICIT  Great app, works fine. Saves me a lot of time. Documentation could have more details though.  
(Version 5.3.1)

KOSOVAR1  Don't get me wrong: I deeply appreciate freeware! But this software only worked for me with about one out of every three audiobook titles I tried to convert. I use Leopard (10.5.4) and the most recent versions of the full QuickTime and iTunes. Two things happened: Either Join Together displayed Applescript errors and could not complete the job, or the joining process hung after QuickTime opened the third mp3 file. Having an enormous audiobook collection, it was imperative that I find some way to join the thousands and thousands of mp3s that were crowding up my iTunes and iPod lists. I'm sure it's the same problem for many other Mac users, so I encourage the developer to fix the problems with this Applescript. When I finally discovered AudioBook Builder, I was really happy to discover that it works perfectly. It also chapterizes the converted audio files, without the use of the Apple Chapter Tool that I was never able to find on the internet. (Hint to developer: Why not provide a link on your website to help people find it?) Well anyway, I was happy to pay $10 for AudioBook Builder, because it helped me enormously to organize my audiobook collection and with minimal effort. In it's current state, Join Together yielded few successes for me.  
(Version 5.3.1)

TJRECK  Works great! I use this often to create joined & chapterized audio books. Keep up the great work!  
(Version 5.0.2)

MACMUSICMAN  This script is a godsend! It's amazing that it's free (although, I like it so much I did send a donation). I listen to a lot of live music and it's great to be able to listen to a full concert without the annoying gaps in the songs.

I can't imagine going back to life before Join Together. Thanks, Doug, and keep up the good work!  
(Version 4.0.1)

SJJ_PUBLIC  I tried running this on three AAC format files, choosing pass-thru. I have chapter tool installed. The script launched QuickTime Player 7.0.4, opened the 3 tracks in it plus created a new Untitled track. It then brought my system to its knees. I waited a while but it did not show any progress in QuickTime Player and continued to completely and utterly throttle my PowerBook G4 1.5 GHz. Eventually I pressed command-option-esc and then wait a long time for the force-quit window to appear, then force quit it and QuickTime Player. I would love to look at this script to see what it is doing and see if I could fix and/or improve it, but unfortunately even though it is freeware it is distributed as a run-only (un-editable) script. I went to the "web site" linked to here, but there is no sign of a "source" version there.  
(Version 4.0.1)