Most Postgres clients have issues connecting to Amazon Redshift. The wire protocol is the same so basic interactions (ex: connect via psql and run a SELECT) usually works but things get hairy when you start doing more complicated things or even just querying the data dictionary (the basic information_schema is there but Redshift has it's own tables for it's specific features).
My company[1] makes a database client that runs in your web browser that has explicit support for Redshift (as well as Postgres, MySQL, and more). I encourage you to check it out.
Thanks for your reply! Never used Amazon Redshift. I'll try to find out what is so special about it.
Edit:
Amazon Redshift is based on PostgreSQL 8.0.2 but PSequel uses libpq 9.3. I'll work on supporting Redshift if it gets enough demands. Anyone who wants a specific feature could fire a request at http://www.psequel.com/report_bugs
Supporting Redshift is actually pretty simple. The only problem is that you need to pay for a cluster for testing. However, since it's pay-by-the-hour you can keep charges minimal (don't forget to delete the cluster when you are done testing!)
Here are a few gotchas with redshift:
1) OID and CTID columns show up in the catalog, but you can't access them.
2) Primary Keys and unique indices aren't actually enforced!! You can insert two rows with the same primary key.
3) Make sure you only access catalogs that exist in 8.0, eg. there is no pg_matviews before 9.3, there's no typcategory before 8.4 etc. (fortunately the PostgreSQL docs are very helpful)
4) When setting the "application_name" connection parameter, PostgreSQL will have to connect twice to a Redshift server. Recent versions of libpq do so automatically, but you should keep this in mind (eg. when using SSH tunnels, or when validating SSL certs)
However, all in all, it's pretty easy to add support for Redshift. (I know because I'm the developer of PG Commander)
My company[1] makes a database client that runs in your web browser that has explicit support for Redshift (as well as Postgres, MySQL, and more). I encourage you to check it out.
[1]: https://www.jackdb.com/