What do you want to know that the Progress and Infor websites don't already cover?
Progress is primarily an "embedded" database. That is to say that it is almost always enbedded as part of an application (such as Infor's), that was built using the Progress 4GL (the new marketing name for the 4GL is "ABL", the new marketing name for the Progress product line, including the database, is "OpenEdge").
This tight integration between Progress, the database, and Progress, the language usually confuses outsiders. They have a really hard time distinguishing between the two and they almost always look at the system through just one lens. You've mentioned other databases so you're probably looking at things solely from a database perspective. That's a mistake -- there is much more to a Progress based system than just the database and, while it is sometimes possible, it is far more difficult than generally assumed to rip out the Progress database and substitute Oracle (plus it saves you nothing because you have to pay for the integration layer, known as a "dataserver", anyway).
BTW, Infor has acquired several Progress application partners, you mention "distribution" so I'm guessing that you're looking at what used to be call NxTrend's SX.e product.
As an embedded database the focus of the Progress db is more towards supporting the needs of programmers and business logic than it is towards supporting exotic DBA checkoffs. For instance Progress supported row level locking long before Oracle did because row level locking is fundamental to OLTP business applications while, at the time, Oracle really didn't care about such things (late-eighties, IIRC Oracle finally added row level locking sometime in the 90s with Oacle 6, MS was even later). OTOH Oracle and the ilk have a lot of very nice features for OLAP that Progress is less concerned about.
You'll also find that, while SQL-92 is indeed supported, that the vast majority of Progress users are much more focused on using Progress from a 4GL perspective. SQL is viewed in the community, at best, as "a neccessary evil". Most Progress oriented people really don't care for it and would just as soon never use it (there are exceptions -- some of whom are quite vocal from time to time in this forum). Progress, the company, has however put a lot of effort into SQL and is trying change user attitudes but it is a slow process. If you start talking SQL to Progress 4GL programmers you'll probably get a lot of blank, or openly hostile, looks.
Progress, the language, is also "ahead of the curve". Tight, natural integration with the database has always been a key feature of the language. You're seeing this today with technologies such as LINQ coming out of Microsoft but this is one of the really big things that originally attracted partners like NxTrend (now owned by Infor) to build their products using Progress. Sure, there are languages that are "better" in various ways. But as a one stop solution for building business applications for resale Progress is the king.
Progress is obviously a smaller company than Oracle or Microsoft. That has pros and cons. The cons are obvious -- they aren't going to spend billions of dollars on R&D or building out every "cool" feature that one of their competitors dreams up. The pros are more subtle -- you can go to user conferences and actually meet, talk to and hope to influence the people who build the software and make decisions about it. They even pop in online from time to time to explain things or help out with problems (you'll see much more of that on PEG or PSDN than you will here).
