My take on it...

Negatives

? Too many different varieties - causes collector confusion

? Too many issuers ? states, banks, rail roads, private companies

? Certain individual issues too rare, not enough notes for collectors

? No established or consistent pricing

? No consensus on which notes are desirable

? Confusion between proofs, specimens, advertising notes, scrip, unissued, and issued varieties

? Poor quality of paper, most issued notes tend to be of low quality

? Poor quality of vignettes in early notes

? Possibility of counterfeits

? Possibility of new hoards of undated unissued notes flooding the market

? Cut or hole cancellations reduces attractiveness and desirability

? Low representation for western states

? No official population reports

? No registry sets at NGC or PCGS

? No established catalog numbers to uniformly identify individual notes

? NGC and PCGS graders don?t seem to use uniform or consistent system for identifying notes on grading labels

Positives

? Many varieties to choose from

? Many issuers to choose from

? Low prices compared to significantly over-priced Federal currency

? Low prices compared to higher population Federal currency

? Low prices compared to much newer Federal currency

? Many unissued notes are readily available in high grades, despite being much older than most Federal currency

? Spectacular vignettes on some notes, much more interesting than most Federal currency

? Historical significance of scenes of daily life during 1800?s

? Historical significance of notes from states prior to their admission as states, when they were still territories of the U.S.

? Interesting vignettes depicting allegorical events and figures

? Interesting signatures of historical figures, mostly hand-signed

? Spectacular color on some notes, much more interesting that most green-back Federal currency

? More variety than Federal currency

? More availability than older Federal currency from 1800?s

? Older than most Federal currency

? More ways to collect, more interesting themes to collect

? More potential for future price appreciation than over-priced Federal currency

? Lack of collectors and investors keeps pricing lower

? PCGS and NGC will grade obsolete notes