With the size of businesses here in Santa Fe (clients are already overstretched in this economy), and the turnover at nonprofits, it's easier to purchase licenses here in the studio and manage them for clients. Otherwise I'd be spending (wasting) way too much time tracking down vital information.
There is the tendency for overkill in managing such information. Rather than use a system that is based on outside services in order to keep track of all info, I have a simple solution: BBEdit. Yojimbo, Evernote, Basecamp and other apps and services have been giving me fits - it's the old story, very familiar to old school webloggers who used the original blogging systems. "What you put in, you can't necessarily get out in any usable form."
So ... I have an all-encompassing project set up in BBEdit, and all my information for a given client goes into folders within that project. This could be duplicated with E Text Editor or whatever such editor you use. All important login/configuration/email setup/etc. materials get added to this BBEdit project as individual .txt files. I carry mine on a protected thumb drive when out and about. Can be easily backed up to a secure (note I say secure) cloud service. [Come to think of it, it could even be handled/extended through Git if one desired. Now there's a way to overdo it.] I occasionally copy off a dated version of all clients and dump the project on an external backup system.
Bottom line: Text files mean I can open that information anywhere - on any system - with a text editor. Small footprint, easy to make backups and keep that information safe. Clients remain impressed I have all their configuration information at my fingertips, no matter where I am, or what gear I have with me.
So I find simple's better. Tip: your naming conventions will matter, when you get in a production rush. Be consistent with filenames and folders!