Latest issue I've found is with a laptop. When TM decides that the share isn't available (e.g. the laptop was taken off-site) it doesn't automatically restart backups when it is available.
When I bring my laptop back on-site I usually need to kick off a manual "Back Up Now" to get things happening again.EDIT
: False alarm. TM had been disabled by some other software I was working on, and stupid me hadn't noticed. Re-did the experiment today: was off at several other networks today, and on return home the backups kicked in by themselves.
But this does open up a disturbing possibility: when visiting a "foreign" network (e.g. a wifi hotspot) if someone can impersonate your networked TM share they could grab a copy of all your data. Given the steps involved in setting up and authenticating a TM share this is probably more of a theoretical than practical risk right now, but it could do with examination.
If the possibility concerns you, manually turning TM off will avoid the risk. But as seen above, you'll need to remember to turn it back on later!