eV3

I decided to buy a LEGO eV3 brick.  They are faster than the NXT brick, have more memory, will accept a microSD card, and run Debian Linux.  eV3 also has 4 output ports while NXT has only 3. But, of course, we have long been using multiplexers to expand both the number of input and output ports. EV3s  are expensive enough that I do not plan to retire my NXTs. (But I will need to redesign at least some of my various robots.)