Root Beer

Since trying Black Bear's Caruso's Legacy Robusto root beer a few months ago, I've become interested in taste testing root beers.  I've occasionally enjoyed various root beer over the years, but this particular brand has really caught my attention.

Recent brands I've tried have been:

Caruso's Robusto - Excellent - nice overall blend of flavors (no corn syrup)
Virgils - Very Good - complex individual flavors
A&W in-store draught - Very Good - quite smooth  
IBC - Good, but certainly not worth its price or trying again
A&W cans - Fair
Barqs - Fair

So far, the bottled brands have been superior to the cans, although I've not tried enough for a good statistical judgment.  At this point, I question if there is a can vs. bottle difference or if it's simply because better root beers are packaged in glass.

Any suggestions for excellent root beers to look for?