You are the first person I heard complain about the Iveco motor (Iveco, not Fiat). The TN motor is bulletproof. I have not heard of anyone having engine or tranny problems on their TN. Around her there are a lot of TN series tractors. Most are F series with the V series making a strong push since NH released them. The TN 95F has the 4cylinder motor that is found in the TL but is in the small F series package. It is a great tractor for doing almost anything you want in a field, vineyard or orchard.
John Deere is second to New holland in this area when it comes to vineyard and small vegeatable farms. The TN and TL are outselling anything in thier class. When you get to larger tractors though, the TS-A is making a very strong push but so far it is still John Deere and Case-IH when you get to the 80pto hp and up. I know of a couple Kubota's in the vineyards, the farmer is not adding anymore and will replace them with either JD or NH machines soon. They have run the Kubota's for a couple years and I do not know if they have had any mechanical problems with them but the operators much prefer the TN and 5000n series tractors they have over the Kubotas (I do not remember the actual model number but I think it is a 5030 size).
There are no other Kubota tractors in the ag industry here that I know of. I see a lot of them in homeowners yards but that is it. As for you comment about the Japs building things that weigh less but last forever, in a lot of ag areas you want the extra weight for traction and being able to handle equipment easier.
I have nothing against Kubota as they make a nice machine. However, they do not make the best in everything. The original poster made up his mind and it almost seems like you are trying to tell him he made a bad decision. There is a reason the TN is selling so well, a lot of people on this board that buy a TN are upgrading from a compact. So far in my own research I have learned that Compact buyers are not brand loyal, some are dealer loyal (which is how it should be). But when these guys get done doing their research they end up getting a TN or 5000 JD. Some get the Kubota just below the M series but very few get the M series. It could be that the Kubota dealers don't want to push the M as hard because they might not make as much or it could be that the M series Kubota is not a clear cut favorite over the other tractors. So far the main complaint I keep hearing about the M series is that it is too light, and the controls are not laid out as well as they could be. With the NH and the JD the complaints are usually about a wire or hose being somewhere that it might get snagged.
To sum it all up, there is not one tractor that comes to my mind as a junk tractor. Nothing on the market today (from the main companies that is) is a garbage tractor. They all make great machines and they will all last a long time. But not everyone is going to buy the same machine. And if we all bought the best tractor on the market we would have bought a Valtra or Fendt (well before Agco bought them both /forums/images/graemlins/crazy.gif).