Only you know if it is a good deal. You say it is in better shape than other cars you have looked at. If it is in good shape buy it, the mileage isn't that high for this model.
I have to repeat that you should deffinately look into the cars record book (or lack there of). These cars a VERY well engineered and built, but if one doesn't maintain it properly, it isn't going to be a good car. Records are proof of good care!!
Bottom line, the 328 (96-99) is a GREAT car. Very smooth six with plenty of torque. I have owned MANY cars (most of them German) and despite the fact that the 3series lack the refinement of some more expensive autos, they seem to me to be a solid value when weighing quality, reliability, work on it yourselfability, and most importantly FUN TO DRIVE!!!