>Until then, I'm continuing to use a Windows package under Wine.
It seems a little incongruous that you're happy to use Wine, but not mono :P.
That said, it does seem a little brain-damaged that Ubuntu have decided to make a required dependency on what should be an optional package, and one for which a C version already exists, no less.
Anyway, your options probably aren't great for running outside Wine: you could install the Debian version of the package, which would mean that you then need to get autopano-sift-c from debian-multimedia, or you could build from source - it may be possible to build from the Ubuntu source package but not include the C# autopano-sift (not sure).
Or you could just continue using Wine. Performance does suffer a little - probably mostly because it's 32-bit - but you're not missing out on a great deal (except that it's butt-ugly :P).