StreamInsight as an ESB?

We've been using StreamInsight for a while to process various events. In the search of a good ESB platform, we also wonder if we could use StreamInsight for the same purpose.

A couple of the key differences between StreamInsight and something like NServiceBus are

1. Max message/event size (StreamInsight is obviously limited in this area)
2. Pub/Sub (takes some work to make StreamInsight work)
3. Easily turn something into a WCF endpoint (NServiceBus is good for this)

But limitations aside, couldn't StreamInsight serve as a poor man's ESB? Or I'm just trying to fix a square peg in a round circle?

I have no experience with StreamInsight but took a look at the documentation briefly to see what it is all about. Based only on this look, it seems to have some powerful event based features, the ability to source events from certain systems using adapters and output adapters for the target system. It seems to be stream based with a query syntax perhaps with a more analytical capability than integration. Aspects of it remind me of EAI tools but my opinion is that process events is a nice feature of ESB it could be a bit of a square peg in a round hole. The various tools do overlap however.

There are many definitions of an ESB on Stackoverflow and elsewhere. I like the simple definition that Hohpe uses on the EAIPatterns website:

http://www.eaipatterns.com/MessageBus.html

The Bus products, including NServiceBus, do over some simiar features, but IMO they tend to offer a more dynamic and potentially fine grained way to integrate. In Nservicebus messages are usually C# POCO classes. Some can be large and it does support a databus. The bus messages are move from endpoints on the bus transactional through a transport. PubSub is built in and intentional. Rather than using adapters, NServiceBus uses a C# API that allows the code to integrate to the bus.

I hope this helps. Regards, Joe.