Few months back I saw TeraData Express Edition. I have no idea of this beast. I want to know whether it still comes with Express Edition and whether it is a good idea to use this database for Windows based mid-sized apps.
I use teradata in my technical support work. I work on database middleware, and Teradata is one of our supported data stores. Define mid-sized? 1-200 transactions per second? I'd stand ANY commonly used database up against that. 10000 tps? Maybe not - maybe you go to the enterprise edition.
It really depends on what you want to do with this application. From an application perspective, a great weakness of Teradata is that it does not support read committed transaction isolation. If you are attempting to use Teradata as an OLTP database, then you might want to try something else. If you are using it to crunch numbers, then yes, go with it. The one issue is that Teradata Express Edition is not supported that well. Express edition is essentially a snapshot of the database for a certain release. If you find and report a bug, it will take a long time for you to receive a fix. Teradata only releases the express editions once per db release. However (imo), if you buy the real version, you will receive a pretty quick patch which will be rolled into the database software.