OOW, I don't own an Enstrom and I haven't flown one yet, but I've been looking at them for some time.
There are a couple of mods that would be nice to have on an F28A, if you can find a machine that has them. First, Enstrom makes a new thicker walled main rotor drive shaft, that eliminates the touchy track and balance problems of earlier Enstroms. New Enstroms are delivered with the new rotor shaft, and earlier machines can be retrofitted with it. Unless this has been changed, the typical unmodified F28A with the older thin wall rotor shaft, will have the historic touchy track and balance issues.
Second, I understand that earlier Enstroms can sometimes have issues with the tail rotor drive bearings. This has been corrected on new machines, and again earlier machines can be retrofitted with the new bearing kit assembly.
Also, I understand that Enstroms can sometimes be tricky to service, and most of the drive system alignments have to be done with precision. So when shopping for an Enstrom, be sure to also shop for an excellent Enstrom engineer to service the machine, because you'll need him. An Enstrom that is properly setup and serviced will be a safe, fun, low cost, and trouble free machine to own. An Enstrom that is not properly setup, will be a major headache to own.