I like your approach. As a maintainer of small projects with very few users I'm not offended by business-like bug reports. But it's very nice to hear someone is actually grateful for my software. (You only need one arrogant asshole demanding support to feel like your software is shit and maintenance is a burden.) Of course you only need to make a good first impression once.

This approach will also help if another part of your message comes off as arrogant. That can happen when English is not your native language.