From what I've seen, or am aware of, there aren't any bugs in the RTB that are serious enough to sway a buying decision. I think I saw that there was a new release due soon.
You may want to hold on to see if this significantly improves the responsiveness of the UI, if that's important to you. At the moment the Keysight is significantly better in that respect.
On the other hand the RTB has a lot more memory, a bigger (touch) screen, built-in (fast) networking.
That is exactly why it is such a difficult choice, the Keysight platform is 6 years old but the offer I am looking at includes all of the following options for the same price as the basic RTB2002 version:
DSOX2AUTO Automotive trigger and analysis (CAN/LIN)
DSOX2COMP Computer trigger and analysis (RS232/UART)
DSOX2EMBD Embedded trigger and analysis (I²C/SPI)
DSOX2MASK Mask limit testing
DSOX2MEMUP Memory upgrade to 1 Mpts per channel
DSOX2SGM Segmented memory acquisition
DSOX2WAVEGEN Integrated 20 MHz function generator
while the RTB is a brand new platform and let's be honest one hell of a scope (yes, I have seen your excellent reviews

) - adding all or even some of the above will more than double the cost of the scope (even if I can spread it over time by extending gradually).
So basically it boils down to the following: do I walk away with an excellent, full option scope (minus the LAN interface) that has proven to be stable but may soon be replaced or do I go for the new (bare) kid on the block that offers the same functionality albeit at a very high upgrade cost?
PS. I did not notice any particular bad sluggishness of the UI for the RTB2000 but I take your word for it that the Keysight is better in that respect (new soon to be released firmware for the RTB2000 might cure that)