First off I would like to say I'm not bashing the devs, It's a great program but it just doesn't work flawlessly (or even close to flawlessly). It was a slight PITA to get the phoronix-test-suite installed, but to get the gui installed that was something completely different.
IDK if this is a problem with php-gtk or if it's a problem with your program but it took me forever to get the GUI to work. I had to manually compile all of the dependencies of php-gtk to get it to finally work. Once I finally got it to work I wasn't that impressed, The input of the program lagged a lot between clicks and atleast the last two tests that I downloaded failed to install. CacheBench gave a non-matching MD5 sum error which was bypassed by copying the archive (and extracting it) to the installed tests directory, the second test that I tried to install was Flexible IO Tester and that failed with errors in the header files (which most likely isnt a problem with PTS).
In closing I love the idea of your program since there aren't that many current linux benchmark tools but it just doesn't work nearly asy easily as it should. It took way too much time to get it to work and when it finally does work half the time it doesn't work correctly.
PHP-GTK is unfortunately a pain to install on most distributions where a package is unavailable. Hopefully more distributions will pick up PHP5-GTK as a package in the near future, which will make it easier on you.
In regards to the input lag of the program, that is being worked on. *Many* calculations are performed with most of the GUI operations and in PTS 2.2 and future releases we are working on optimizing and caching some of these paths.
In regards to download failures and MD5 match fails, please report them. In those cases it's a matter of the mirrors either going down or changing the files.
The interesting thing is that Arch Linux provides packages for all of the dependencies of PTS but they wouldnt work correctly with it, php-gtk was the main problem since it kept giving the API mismatch error.