@mrmikel - my issues haven't been that Sigil crashes particularly often - it is stable in that regard which is a credit to Valloric. It is that it discards content or changes silently - which is the most dangerous kind of bug because you have to go looking to find out what you are now missing. This most frequently happens when using merge, but can also happen when using find/replace (where it does not actually do the replace which you only find out when you put focus back on the code view). I try to work around this now by saving before any merges and then double checking the content but every now and then you forget and get bitten badly.
Note also that it was not my intent to in any way turn this into a "Calibre is better because" type thread. I merely wished to indicate for any interested what attracted me to contribute to one project versus the other and it was the most recent example for me to use. Like any app ever written Calibre has pros and cons be it user interface based or technical. I just wished to share "from the outside" why I chose not to get more involved in the Sigil development, my perceived challenges for whoever does take it on and it's future as an OSS app. As always they are just my opinions which everyone is welcome to agree or disagree with
For myself, I would not care if Sigil became closed source. If Valloric in 2.5 years has struggled to get contributions, then both finding a maintainer / magicking up some contributors in a few months is a big ask without commercial involvement. Like mrmikel as I put in my first post here, if I had spell checking, the option of ncx mgmt and some bug fixes plus multi-select for merge/delete and that is all I want from Sigil - provided someone is maintaining the app I could care less whether it is closed or open source personally in this case.