My main hesitation is the proprietary firmware. Now I'm not going to disagree with anyone arguing that Cisco knows what they're doing and is competent at putting together firmware for the hardware they sell. Nor will I disagree with anyone arguing that open source is not a magical talisman ensuring quality. No, my main concerns are a) timeliness of critical updates, and useful lifetime of the hardware vs support lifetime.

Being open source cannot prevent bugs, but once found, fixes tend to become available quickly. Also, I have found that the useful lifetime of computing and networking hardware tends to exceed the period of time the vendor will offer support for it. I have gigabit ethernet switches I bought years ago that still work just fine, even though they're no longer sold. That's what I love about OpenWRT. The hardware my home router uses is discontinued, but still does the job just fine, and I can still get updates when I need to.

That said, I think I will be checking the SG300 out. Thanks for the recommendation.