This article by Dan Vanderboom is one of the best pieces of writing I’ve seen to explain why Oslo is important. Here are a few quotes, but you should take the time to read the whole thing.

Oslo respects this need for choice by offering support for building both visual and textual DSLs, and recognizes the fluent definition of new formats and languages as the bridge to the next quantum leap in productivity…

That’s one place Oslo provides value.  With the ability to define new textual and visual DSLs, rigorous verification and validation in a rich set of tools, the promise of Intellisense, colorization of keywords, operators, constants, and more, the Oslo architects recognize the ability to enhance our development experience in a language-agnostic way, raising the level of abstraction because, as they say, the way to solve any technical problem is to approach it at one higher level of indirection.  Unfortunately, this makes Oslo so generalized and abstract that it’s difficult to grasp and therefore to appreciate its immensity.  Once you can take a step back and see how it fits in holistically, you’ll see that it has the potential to dramatically transform the landscape of software development…

That’s all well and good for DSLs and language enthusiasts/geeks, but primarily perhaps, Oslo is about the creation, exploration, relation, and execution of models in an interoperable way…

Oslo provides interoperability among models in the same way that SOA provides interoperability among services.