I just added a third R15 to my home setup. It was more of a stopgap until I jump to HD around Christmas time (then I'll have a two HR20, one R15 config). This assumes that I can get my hands on an HR20 when I want to.
For now, this is what I have
Living room -300, 0x104B updated last in September
Master bedroom -500, 0x10E8 updated last in October
2nd bedroom (installed Friday) -100, 0x1022 never updated
I did the 02468 trick this morning on all three machines but it just downloaded the existing software. This is getting more and more difficult to keep track of!