Double-spend detection is the only real answer to speeding up trust in Bitcoin transactions, not decreasing block time like Solidcoin has.  There are at least two ways that it could be implemented:

1) Listening nodes (http://bitcointalk.org/?topic=423.msg3819#msg3819)
2) Querying mining pools (https://bitcointalk.org/index.php?topic=40264.msg494150#msg494150). A less rigorous version of option 1 that focuses on tracking estimated total hashing power working on a given unconfirmed transaction

The methods could be combined. Of course there's also the option of building true instant transaction layers on top of bitcoin like MtGox and Open Transactions servers.  Double-spend detection, as originally envisioned by Satoshi, would also largely neutralize any problems arising out of sudden drops in Bitcoin hashing power.