Parts shouldn't be a major issue as all GM dealers will honor Pontiac stuff. The only caveat is that anything Pontiac specific will likely have to be ordered instead of in stock so there will be that down-time to consider.
Pontiac resale value has always stunk so I don't see it getting much worse :banghead:
the thing about the dealers not having the parts in stock is definitely true. They've had to order bunches of parts for mine so most repairs that involve replacing a Pontiac-specific part take at least 2 days. At least the dealer over-nights the parts though and I don't have to wait a week. The car IS supported and the parts aren't necessarily hard to get, at least.