I have a 722D and a 725D, both front mount diesels. I love them. They are rugged but comfortable, and do a great job on the lawn and trails I mow. I treat mine like a brush hog sometimes, but have never had any major issues. I had to replace a solenoid on the 722D after 8 years I think, and it was only a few bucks. The bearings on one rear wheel on the 722D also needed replaced once, and that included some spacers and other parts but was still less than 20 bucks I think. I tow a trailer with them, use them to spread fertilizer, and tow my 12' boom sprayer. On the down side, like any diesel they are heavy. That's about it.
Dealer support is important. I have a couple I can use, and have more GH dealers around me than Kubota dealers. My closest Kubota dealer is also a GH dealer, if that tells you something.