While I find myself choosing PSUs of the non-modular type, I've had some good experiences with modular PSUs. I have an Antec Neopower 480 that I've owned for about 3 1/2 years that has really served me well. I've not had a single issue with it. I use a Coolmax CU-600 (which is modular as well) as my test PSU that I run my water cooling loops after I've freshly installed some new component into them. I cannot discount other peoples concerns though.
Some of the most reputable power supply companies have modular lines of PSUs: Mushkin, Thermaltake, Enermax, Silverstone, Coolmax, XCLIO, MSI, Antec, OCZ, Raidmax and FSP