The TD-D has been in the Case lineup as the JX for some time now. The guys I know that own them love them. I have never used one yet but from looking them over they are built very solid and are more in line with the TL then a TN. The TN has a no frills counterpart known as the TT series.
Both the TN and TL series are great tractors and are more geared towards operator comfort while the TD-D is geared towards cheaper power with decent operator comfort. It doesn't have all the bells and whistles like the TN and TL but for its price it is very hard to find much wrong with it. The only thing I don't like on the TD-D is the rear cab lights look like an afterthought. They just don't blend in and if you like to run into tree limbs I don't think the lights will hold up very well as they stick out and up away from the cab.