Signed up to JustHookUp exactly one month ago today so I could do a direct comparison with Flirtydater.com, which I joined at the same time after reading a few good reviews. Hopefully my doubled subscription costs will help some of you lot!
Main advantage of JustHookUp is the mobile app - but have to say the Flirtydater mobile experience is also fine when using their mobile site.
Disadvantages are that I didnt get laid (I got laid once with Flirtydater after two and a half weeks and drawn a blank since). Also, for me, the JHU app sends too many needless push notifications and I wasnt a fan of the search function, but thats a small nit-pick.
Winner: Fairly impressed by both but Flirtydater shades it, ill take actual sex over an app any day of the week.