Damn; was in the process of purchasing, then I realised it requires 10.10. If/when I upgrade, I'll probably buy - looks really nice and effective, and genuinely fills a need (can't quite believe this isn't built into the OS, tbh).
Sorry that it requires OS X 10.10. I do know that many people haven't upgraded for various reasons. The thing is I wrote the app with Swift and I won't be able to support Mavericks until I can submit the app with Swift 2.0 which lets me target a different OS version. If you want then you can subscribe at the bottom of the page and I'll remind you about Gestimer once OS X 10.11 is out.
Would you mind sharing any of your experience building it with Swift?
It's just been really fun. I don't mind ObjC but Swift feels so modern and nicer to type. One problem might be that Swift is constantly changing and that means you need to update your code base whenever you want to use the latest Xcode. I don't mind though because that's also a great way to learn about the changes. Ask away if you have any specific questions.