We had a Nimbus 3D in our club.

Rigging is fairly easy, but time consuming because of the number of parts and control connections. The inner wing weighs roughly 85kg, which is fairly heavy but it is at least not very big.

The Nimbus surely is not a beginners glider but really nothing to be afraid of. Control responsiveness is slow but effective. Stick forces are normal and not particularly heavy (as in the single-seater Nimbus 3). Landing flaps and effective spoilers allow for good approach control (better than you would expect from such a large glider).

There are some quirks: In landing flap configuration the aileron effectiveness is reduced. Especially in cross wind conditions you better land in thermalling flaps (which works absolutely fine). With full water ballast the wings loose some ground clearance. On aerotows keeping the wings level requires some attention. Also on landing I came across some club members who had consistent difficulties keeping the wings level.

Winch launching without water was never an issue and common practice at our club. But, you really don't want to drop a wing!

The series of structural failures with Nimbus are all(?) related to high altitude high speed flying. I would not worry too much unless you plan to go booming around Africa, Australia or western US.

Maintenance scales with the glider. Lot's of parts and fittings which will wear and need your attention sooner or later. Especially on used gliders the small issues have often started to pile up and keep you busy.

From a design perspective the Nimbus is pretty robust. The tailplane is the mediocre Schempp-Hirth design and the water ballast will start leaking sooner or later (as in most gliders). The outer spoiler cables tend to break or lose their adjustment. Other than that the Nimbus is just a bigger Janus/Duo Discus, which are both proven and popular designs.