Sorry, but I'd have to say that Igor is pretty shabby in comparison to Finale. 1. It's incredibly slow. One person on the Igor mailing list tried to add about 500 measures to a large score. In Finale this takes about a second. In Igor, it took over 8 hours. I have three extremely fast computers, two of which have 640MB of RAM. On the fastest of them, it still takes up to a second to enter a single note on large scores. And that's after following all of the speed tips. On the "slower" PIII 500 with 320MB of RAM, it takes up to 5 seconds.
2. The program was released two weeks ago, and they've already released 23 patches!? With Finale that's called BETA software. It doesn't belong on the market. In the first thirty minutes of trying Igor, it crashed 10 times on me. People were posting saying that they had found the special ways to avoid crashes by not doing certain things or using certain tools.
3. Finale can do all of the playback things you mentioned. Also, Finale 2002 has just been released.
4. Igor's support for recording in real time from a MIDI keyboard has been called so terrible that it basically can't be considered a feature.
I could keep listing all night long, but instead I suggest just trying the demo!
There are a few features in Igor that Finale lacks, but there are literally hundreds (possibly thousands) in Finale that Igor lacks. If you believe Igor is superior to Finale, be prepared to back up the statement.
