I have a Logitech F310 gamepad which supports both old (DirectInput) and new (XInput, ie. XBox360) games. In the XInput mode, Windows seems to consider it as a XBox360 gamepad, and it seems to be 100% compatible with it in all XBox360 controller games I've tried. Good purchase.
For a GOG gamer, both modes are quite important, unless you want to use something like XPadder with many of your (DirectInput) games. For example the Prince of Persia games, some of them really need the legacy DirectInput mode, while the newest one is definitely made for XInput/XBox360 controls. So when I play those games, I need both modes for different games in the series.
What I think about gamepad controls in games?
Pros:
+ Easy to learn the controls by learn-by-doing, as you don't have to go through the whole keyboard to find all the keys. This is the case at least with newer XInput games, with older DirectInput games there is more variation, making things more complicated (ie. with newer XInput games, the default gamepad controls are usually fine; with older DirectInput games, I quite often need to remap all the PS2 style gamepad controls anyway for some reason, the default setting just feels unnatural quite often. Possibly because they were not meant only for PS2-style gamepads, but also legacy analog flightsticks).
+ Can play more easily laying back from the computer, even on a couch. No need for a desk.
+ Analog movement is useful for many games, and great for racing and most flying games.
Cons:
- Sucks for FPS games or other shooting games where you need to aim a lot, period. Mouse aim, mouse aim, mouse aim. This includes also Mirror's Edge, I much prefer the mouse+kb controls to the gamepad controls, just because of the aiming (even if there is very little shooting).
- It is pretty restricted how many fingers you can use for controls. Even with the modern gamepads with four shoulder buttons/triggers, usually your mere thumbs do like 80-90% of the controls, alone. And shoulder buttons with the index fingers, so most of your fingers are useless, just gripping the gamepad.
Sometimes this matters, as you can't obviously press two or three buttons at the same time with one thumb, or use an analog thumbstick and push the face buttons at the same time with one finger either. That actually mattered to me in games like Halo 2, where with a gamepad you couldn't practically aim while you jumped, while with kb+mouse (on the PC version), you could do that effortlessly.
Anyway, I prefer playing many games with a gamepad nowadays. I was actually surprised that even such old game like MDK, which I earlier finished with kb+mouse controls, feels now even better when I was able to map the controls to the gamepad (that took a damn sweet time, lots of trial and error before the controls felt fine. I had to put strafe keys to shoulder buttons etc., as the game does not let you map any analog axis to strafe IIRC). The game doesn't need that precise aiming, so in its case missing mouseaim doesn't matter much.