I use the payware version this app to remotely administer two VMware virtual data centers, which means connecting to Windows Server 2012 over a VPN. My work is often mobile, which means I may be connecting from my home office with fast wired networking and reliable VPN, or from a coffee shop or hotel with mediocre wifi.
The 2X client works reliably for me and has provided better performance than Microsofts own remote desktop client for Mac. How much better depends on circumstances and on how youve set your session preferences, of course. I wouldnt try running 3D games remotely with this or any other RDP client, but for VDI infrastructure and typical office productivity apps, or for the kind of sysadmin work I do, if youve got decent bandwidth this client is a good choice.
I havent tried the 2X App Server, so I cant review that. What I *have* tried is connecting to remote Linux desktops using the RDP protocol. You just install something like "xrdp" daemon on Linux (its available with most popular Linux distributions, and very easy to configure). 2X works just fine in that environment, and Ive found it to be more responsive than either remote X11 or VNC protocols. Most Linux sysadmin work is done with SSH, but if you need a GUI for some reason, this is a good alternative.
Several weeks ago I encountered a minor bug in 2X, and reported it to tech support. I received a response a few days later from a real person, and we exchanged a couple of emails back and forth. They were in the process of working with me to isolate the cause of the problem, when an update to the software fixed the issue entirely, and I was able to close the tech support incident. Apparently I wasnt the only one to report it, and the developers had already been working on it. The bottom line here is that this company pays attention to user feedback, and they fix bugs. Thats all I can ask of a software provider.
There are perhaps a couple of things I might change in the user interface, but UI design is by definition subjective. Everything works fine, just a couple of the connection settings fields are labeled in a way that I found quirky. Once you understand what the field actually does, using it is quite easy. In other words, experiment with the settings a bit as you familiarize yourself with this app.
This app isnt glamorous, but it works well, is reasonably priced, and is well supported by its provider. Recommended.