Popfly is Microsoft's venture into the world of visual mashing applications, and is a Web-based offering like Teqlo and Yahoo! Pipes. Currently in invitation-only alpha release, I signed up to the waitlist for Popfly about a week ago and my invitation to join arrived today. In between time I had seen this review on a Wired blog, so I had already reduced my expectations a bit of what I might find with this alpha release.
What has lived up to expectations is the interface, and while I can see a fair bit of room for improvement I imagine as a Microsoft product this can only get better. However, I won't hide my ongoing disappointment of Web-based applications that require the latest browser (Internet Explorer or Firefox only) and yet another plugin (in this case Silverlight) to operate correctly.
Unfortunately the main problem I had initially was getting mashups I tried building to do something and then run. My browser froze a couple a times or appeared to do nothing. I had a little bit better luck with mashups built by others, and then when I tried some simple mashups using RSS feeds. But with limited debugging tools or information, its hard to know as a user what was going on (or why something wasn't working). I did at least manage to get an RSS feed converted into a table. Problems with the mashing interface also caused a few problems, such as blocks that created outside the middle of screen and become inaccessible - all I could do in that instance was start over from scratch again. BTW I eventually worked out that the RSS input is a bit picky doesn't accept anything other than a true RSS feed, so forget Atom or even Feedburner!
This means it is relatively simple for people who can script to add new functionality or data sources into Popfly. Hopefully because of this we will see more than just mapping and photo mashups, such as more options for displaying mashed up results in graphs, dashboards and spreadsheet-like tables. From an enterprise perspective, that really is an exciting prospect.
Overall, while I still not convinced based on any of my experiences to date that these types of tools will ever be easy enough for anyone and everyone to use (also see the "Difficulty Curve"), Popfly is another step in the right direction towards that vision.