The OSX 10.8.2 over local USB connected SATA drive is working quite well. The 10.8.2 is a big improvement in local USB operation reliability. In previous OSX releases like 10.[67].x even the TM startup was an issue.
Still in 10.8.2 the over the ethernet backup speed is too slow - 2MB/sec would translate in a week of continuous backup for a standard disk that is shipped with Macs.
My alternative for over the network backup is rsync over ssh to linux running jobs from cron. The target disk is LVM2 that supports snapshots that are created also from cron jobs. In this way I just maintain directory for each Mac on the LAN and run incremental rsyncs. I keep two weeks of snapshots and expire older ones - kind of DIY NetApp. Unfortunately this is only for geeks and it is a project in itself while this should be plug-and-work directly from Apple.