Luggage solutions are very much a personal preference thing. I've done the tank bag thing, and the tail bag thing. For my uses, I've found a backpack to be the most convenient and useful.
The reason is simple: It's one less thing that you have to fiddle with on the bike. Get to the store, the office (or whatever destination) and you just hop off, lock the bike and walk away. Time to leave... hop on and go. No worries about security when you stop for lunch. Etc. etc.
For those unexpected (or even expected) trips to the store, I keep one of these in the bike's tail. Thus I always have a way to carry stuff, ready to go. I use this only for those occasional needs. Definitely not meant for everyday duty, but super-useful when the need pops up.
http://www.treklightgear.com/bindle-daypack.html
For regular use (commuting), I have a Kriega R25 backpack. I thought for a very long time about this before buying it, because Kriega gear is so expensive. I'm glad I did. It is, in a word, perfect. The chest suspension thing is no gimmick. It really does work. All-day comfortable.
Regarding saddlebags/tail bags, I've had a few variants over the years. None have really stood out. All have worked adequately. I don't think it matters a whole lot.
My most recent, which I still have, is a Bags Connection Cargobag. Good for touring. Wouldn't use it as an everyday thing.
http://www.twistedthrottle.com/bags-...luggage-system
