Does that mean Hostbill is much improved and nobody has anything to complain about
Yes... and no. It has come a long way and is way more stable, reliable and powerful than it used to be but the forums are also quiet because most users that remain have developers and do not need assitance.
This forum is like a deserted wild west town with tumbleweeds floating by.
One of the reasons it is so quiet is that notifications seem broken - most people don't notice when their topic has been replied to.
At least 21 companies use Hostbill and think its great
I think most companies that actually use Hostbill are not listed. My employer is not listed and I know that one of the major cPanel license resellers (buycPanel) uses them too - and they aren't listed either =)
Is it worth a try, or should I stay well away?
Depends on what your needs are. If you elaborate on which features you need exactly, I could probably give you a better reply. We came to Hostbill in 2013 from the now-defunct AWBS billing system and WHMCS simply did not work out for us even during testing phase.
I often wish I could change but NO billing system is perfect. What I wish more would be to have access to source code to add my own features or fix problems but none offer that much flexibility....