I have the B2650, R4 tires and the 72 inch mmm. I have been very pleased with this rig for mowing. I purchased it with the Loader, the QA bucket and a 72 inch grader scraper. As Toolguy says, you will leave tracks if the ground is soft. The ground engaging wheels on the mower deck do leave lines in the grass, but I think the cut looks good. For me, it was a bit of a trade-off. I traded up from a BX 2350 with a 60 inch deck. I never liked the abrupt stop of the HST that plagued this model. We have several small fenced paddocks that were too rough to mow with the BX, but too tight to mow with the bigger rig we have for field mowing (MX5000 with a 72 inch Woods BB720) So far the B2650 has been a good fit. It has a very comfortable seat. It is also a lot more maneuverable than I thought it would be. I mow around the house with the B2650. You do have to be a little careful when you are on uneven ground. I have the mower wheels set to cut at 3 inches around the house and with the 72 inch deck you can find yourself scouring the ground if the deck is straddling a hill. When I switch over to mowing the paddocks, rather than getting off of the tractor and having to pull the pins out of the 4 deck wheels to raise the height of the mower, I just raise the deck a little with the three point hitch lever. I asked my dealer if this would be ok since the deck is not a suspended deck like the BX was. He didn't think it would be a problem as long as it wasn't too much. I am really only raising it a bit more than an inch or so. The cut looks good and it hasn't caused any issues.
Hope this helps.