Best bet is to refer to the
http://www.animeondvd.com 
website which lists what anime is licensed where. 
I usually collect the US releases but rarely 
listen to the dubs. 

However, the subtitling on some of the HK stuff 
is just awful I've seen enough of my friend's 
DVDs. Image quality is quite variable as well. 
Some excellent some really bad. And as the first 
poster indicated - many are bootleg.

I have one DVD in my collection from HK and that 
is the 3 Part OVA Read Or Die. (Simply because I 
despaired of Manga Entertainment ever getting the 
R1 copy out before 2005). That has excellent 
video quality and very good but small subtitles.