Thalictrum can be cut back after flowering or delayed until the late winter/early spring as the foliage and seed heads remain attractive. I tend to leave the stems and seed heads which are quite attractive and usually I am rewarded by seeing small birds perched on them. Thalictrum can self seed but not so much as to be invasive and is trouble free.
If you do need to divide a clump, this is best done early spring or early autumn. However another advantage of Thalictrum is that it can be left for many years undisturbed and does not need routinely to be divided, unlike some other perennials. It really is maintenance free.
I know of no down side to growing Thalictrum and it is just so pretty. The image left is of a lovely white variety known as T. delavayi 'Splendide White ' which is fully hardy and tolerant of dappled shade, preferring soil which is on the damp side.
The easiest way to propagate Thalictrum is by division in the spring. Dig up an established clump and divide cutting through the clump and roots, and re plant separately. Water well and they will establish easily.