[whpalmer4]

You can only switch sync methods after syncing all of your devices, or you risk losing changes that hadn't been synced. Also, the first sync after you switch back to MobileMe is probably going to be slow if you have a big database, as it will need to store the entire database again. Given that, the convenience factor of switching sync methods frequently goes way down. My suggestion, meant with absolutely no disrespect, is that this practice is probably an "if you have to ask, this probably isn't for you" sort of thing...

One thing that helps keep syncs going a little faster is to only have one device contributing changes at a time. In other words, after you make some changes on your iPhone, try to get the devices synced again before you make changes on one of the Macs. You might also try syncing the iPhone first when it has been more than an hour since all of the devices have been synced (which you can check in the Sync preferences panel client display). This is a bit of speculation as to whether it will make a difference in your case, but the last client to be synced will be the one rewriting the database after compaction, and your Macs may have a faster upstream connection than the iPhone, not to mention a much faster CPU.