I don't know of any other tool that works as well as Wireshark for packet capture an inspection. It's extremely easy to get up and running, and even with little to no knowledge of how to use the tool, you can be looking at all the traffic coming off a network interface.
A more user-friendly interface would be nice, but then again it is not really designed for those who are not quite comfortable with this type of software.
Changes to functionality on updates - this can sometimes happen unexpectedly and can be an annoyance.
It's very simple and easy to use, although individuals not used to managing and administering networks would take some time to get familiar with it. Once they have mastered use of the application, it's easy to stay knowledgeable about it, iteration after iteration. It is well supported online through an open-source community network of professionals who are helpful in imparting knowledge and in providing assistance.
I don't believe Wireshark has "true" support as the software is open source. However, there is an active & friendly community around Wireshark that are more than happy to help answer questions. From a comprehensive Wiki and FAQ section on the site to the Ask a Question forum and bug tracker section, there's plenty of support options to make sure your questions and issues are addressed.
I haven't used other products that are similar to Observium. Observium is an open tool, with a robust feature set. There are elements of comparable monitoring across other tools, but nothing I've seen that is a complete parallel in terms of feature set and visualizations. If I were asked, I wouldn't have another tool to recommend over Observium.
Wireshark is a free tool that came highly recommended by one of our former network security consultants. Using the tool he was able to resolve all of our higher tier network tickets, so we observed first hand why we needed to add Wireshark into our toolset. We received in-depth instruction and training scenarios that demonstrated the effectiveness and power of the product, so we didn't spend any time reviewing competing products.