Hi,
Like yourself I'm an iPhone 2G user, and I previously used SwirlyMMS2 on 2.2.1, but when upgrading to 3.0, was unable to install SwirlyMMS since it has not yet been updated to be compatible with 3.0.
This link here details a message users of SwirlyMMS2 were sent by the creators explaining that a new version is in the pipeline, with 3.0 compatibility as well as many other features:
http://www.applei.ph/one/component/o...d,54/id,43664/
The SwirlyMMS people have deliberately blocked the app from being able to install on 3.0, I can only assume that this is due to compatibility issues, and I for one am holding off for the update before attempting to install it. However, I have heard about some people using cracked repos in order to install it, and that it works mostly fine.
So, SwirlyMMS2 is going to be upgraded somewhere in the (near?) future. Those who had already bought it previously will be able to update for free since the purchase is tied to the handset, not the software. I would speculate that the original SwirlyMMS will not be updated, and SwirlyMMS2 will be the only version made compatible for 3.0, which, to those who haven't bought it, will cost them $12, but I for one think this is a small price to pay to get MMS capabilities on the 2G.
Hope this helps.