I did about 10 captures (small, big, with javascript, java, 
php, asp and Flash), interrupted some of them, continued 
them, updated some of them a few times, modified the scan 
rules and resumed, updated ancient captures with 
HTTrack3.23-ALPHA-keepalive-noV6+swf.
When having problems, I switched to the 3.22 version but 
never noticed a better link testing or a better result (the 
problems were due to site conception, javascript parsing or 
php or mv(?) files).
The ALPHA version seems to be safe and faster but I 
wouldn't garantee. I didn't notice a better link testing 
but it surely depends on the site captured.
As of today, I would say it shows no extra bug or extra 
crash and is at least as stable as the previous versions. I 
will send a message if I find any problem or bug.