I speak from recent experience, although I can't comment about the G25 as I don't own one, have a quick look at my thread linked below regarding some Saitek eqpt:
Saitek R660 - (Saiteks latest wheel)I tried 4 feedback wheels in a similar price range over a period of a couple of weeks making sure I bought the right one..
Saitek R440
Saitek R660
Logitech Momo Force
Logitech Driving Force Pro
To summarise, the Saiteks are very plasticky and the FF is either too subtle or too harsh. You can obviously alter the settings in the control panel but the steps are too great.
The Logitech Momo is a decent wheel but the Driving Force Pro with 900 degree rotation beats it hands down. I ended up buying the DFP second hand from ebay and would recommend that over a brand new Saitek every day of the week. The FF is spot on, the resistance is good and the degrees of rotation can be set to whatever you want..i.e you don't have to use 200, 600 or 900 etc, and it works fine with Vista. All the wheels are approx £50, the DFP and Momo are obviously slightly more expensive than that if you find one brand new.
If you have the budget, I've no doubt the G25 is at another level, I'd recommend you try before you buy if possible and make sure you get the one that's right for you.