Well, for me, FTM & Ancestry is certainly covenient(Despite the price) and very easy to use environment and with the built in bowser and figuratively speaking, easy to take along your workspace as you visit different sites. Not that I use just the internal browser, I usually have IE and Firefox both going with 4 or 5 tabs a piece.
I have been experimenting with the custom facts feature you had mentioned although I am using just one new fact entitled "Public Trees" to allow me to at least link to all the family trees associated with a particular individual from my file for further research.
Whats nice about it is that it when I view the fcats for an individual, there is just one line entry for "Public Trees" and because I have linked that fact to eacb individual family tree set up as a "source", it actualy now shows the number of trees that reference or contain that individual.
Now a simple double click and I'm looking at that tree.
The only downside is that when merging a family tree as you know, a boatload of facts come with it. I now in setting up the new public tree as a quasay source, I have to go into the links and unlink all the garbage links and then ccreate a new link to the new "Public Trees" link for each person that came over in the tree.
It's not as bad as it sounds.
As a simpler alternative, I am experimenting with copying the URL and pasting a shortcut to the URL in the media folder for FTM. Now, I can create the source as above, but instead of having to setup new links to "Public Trees" for every one, I can now add the media shortcut to the media tab of the source. It saves some time, but I still have to go in and unlink all the bogus facts from the source, so they will not show up in the list of facts for an individual.
I'm not sure I could follow what just wrote myself, but I'm still working with it and in the process getting a pretty good handle on the relationships of sources, facts, individuals, etc.
anyway, if your curious how it turns out, I'll keep you posted.
save some public tree information and so far, I'm liking it.