My advice is to download and try the free version. Especially like in my case, the IDE code editor cannot keep up with my typing speed. I worked around by using Atlantis Wordprocessor and paste the code in Xojo. Make sure you at least test for this before you buy your renewal. If as in my case, the editor is so slow, it can slow you down severely. If you are comfortable with Xojo code (I am sure you do), then this workaround will work for you too.
I like to add that in Sublime Text Editor and many others, you can create your own code libraries. In this way you can syntax coloring your code, so you check easily for mistakes. In Atlantis I also created my own dictionary for this. It is just what you prefer.
I am not 100% sure of whos faultive, but I get slowliness when using FireFox and a certain external HD. When I quit the former and remove the later, speed comes back.
Did you try to run Xojo as the only application / no other hardware connected to your computer ?
And what about a boot in the Windows fail less mode ?
RB2008 ran fine on a Pentium 4 whereas Xojo 2018’s IDE would like in my experience an i7 and if in Linux VMs, 16GiB of RAM 'cause it mysteriously leaks so I give it 12Gig and reboot my VM often! With an SSD that only causes a 30-second interruption but it’s worth it as I very much like Xojo, and it will be far-and-away the best RAD for Linux (hobbyists and professionals alike) when the leak is fixed and cutting, pasting and typing are improved.
However what you are seeing may also be network-related on a slow machine because unless I am mistaken, the IDE is written in Xojo which is very important for Xojo Inc. dog-fooding the platform IMHO. But for multi-processor performance looks like the IDE uses loopback network for its interprocess communications – at least on Linux. That may explain the slowdown vis-a-vis Firefox usage on a low-spec machine.
I never have an issue with any of this in my own apps because the Xojo IDE is far more complex than any of my UIs which are mostly Web and console anyway. I think an IDE is one of the most demanding UIs possible and few developers would encounter the same challenges as Xojo Inc. so they are ahead of the game so to speak, although I imagine people writing moderately complex UIs on a Pi might encounter similar inter-process challenges when the UI becomes single-processor bound. (Use Firefox with a lot of tabs and the Pi becomes unusable anyway.) The moral of the story is the Xojo IDE definitely benefits from an i7 so that’s another thing to consider when upgrading from RB.