I don't have them yet, but I have heard good things about them from people who actually know what they're talking about. I spent some time with a sawzall and an empty clip, and anything that isn't the frame rail isn't very stiff. If you've ever seen a bare chassis, you can see why they work. The main rigid member that run front to back is the lower frame rail (where the crossmember bolts on). There is also a smaller, thinner, and much weaker rail that runs from the strut towers to the firewall, down where the doors bolt on, and turn into the rockers. The problem is that the entire weight of the front end is suspended from the strut towers, braced by that weaker rail. Reinforcing that point will help the chassis resist (or push back) the large/sharp impulses at the strut towers like those induced by stiff suspension during agressive manuvers. Making the front chassis stiffer improves a lot of "feel" qualities like turn-in, feedback, and ride quality. Judging strictly by pictures, I'd stay away from the L-shaped ones like Tanabe, as they don't look like they'd be very stiff. I like the looks of the SPL Parts and Nagisa ones.

Here's a link:
http://www.nissanperformancemag.com/february04/240sx/

By the way, the Cusco triangle brace in my WRX was awesome even on stock suspension. I would wager that on a hatch style car the feel would be much improved with one.