Branchwalker, when climbing a tree you work from the inside out. With a bucket you work from the outside in. It sounds like you already figured out the 15k thing. A forestry truck, with the boom mounted behind the cab, is good for working off roads or anywhere you are going to the side. In residential work you will find that most scenarios the room is tight and going off the side isn't always possible. Having a chipper on back means less vehicles but it also means you will need more room in your work area to pull truck AND chipper up to the tree. Then when dumping you need to lower outriggers, raise the boom, raise the box, raise the outriggers, pull forward and then put this whole thing back. You will only be able to dump on very level and solid areas. Now if you get a rear mount truck with over center ability, your reach will be greater and take up less room. You will have to have another vehicle for clean ups but just charge accordingly.
As far as maintenance you should find a reputable mechanic that is certified for that boom for your yearly inspection and a dielectric test. Check into these numbers to figure out your costs.
As far as a track mount I believe they would be OK for removals but trimming may be an issue because of their non over center capacity= limited reach. Look at the paper work as to how much reach and in what direction they go. They maybe tall but it is nice to have some room below you that isn't your vehicle or base.
There isn't a one boom is great for all trees. There like golf clubs, one is great for this and another is good for that. Long story short is that I believe that a rear mount, over center boom will give you the greatest versatility.
