I have 2 115s, 1913 and 1915, both with Tiffany/Gingerbread decals. They are as rock solid and dependable as 66s and 15s, and are incredibly smooth with the full rotary hook. The bobbins are still manufactured today, as are cases. I bought bobbins from Cutex, and they work very well.
The 115 does not have reverse, however there are a few different ways to lock your stitches without having reverse. Shorten your stitch length at the end, or turn your work 180 degrees and stitch back, or lift the presser foot, pull back the fabric, and restitch.
I use one as a hand crank, the other is a treadle. I am new to treadling, and have to report that I have jammed my 115 by inconsistency in my treadling technique. Always the Singer handwheel must turn towards you! Some minor dismantling of the bobbin guts, removing the caught thread, and reassembling was involved. Has my technique improved? No. It is very way to treadle fast, but not as easy to go slow and remember to continue using the full range of the pedal, which is where my mistake occurs.