Sorry to restart this discussion, but I've just got my Aibo (210A) from Ebay, and I thought this was an interesting thread anyway. I was quite prepared for something that was more of a robot and less of a life form than Pleo, and in many ways it is, but I think much depends on the software. On something like Party Mascot it's most definitely a robot, showing off it's moves and bleeps to order, but on some of the other software like Life or Explorer I saw more of a character coming out, and much as I love Pleo I don't think you get the depth of character you can with some Aibo software, and there is a wider range of programs and characters to chose from so that you can have the Aibo you want. Yes, you do pay for it, but these days you can get a used Aibo 210 for not much more than a new Pleo.
When I first unpacked the 210 and switched it on it had an Explorer card in it and it was not a happy Aibo. It ignored me, refused to do what I asked it and then turned its back on me. I asked it if it was alright, and it shook its head sadly, no amount of petting and calling it a good boy seemed to cheer it up and it eventually put its head back and howled. It was only when I tried 'good girl' that it started to cooperate - stoopid me, it had never occurred to me that it was a girl! From that point on I fell for Aibo.
Now I love Pleo, I love Iggy's endearing character, I love the way he walks (especially from behind), and I love the little quirks and odd moments you get with Pleo. Pleo is much more immediately lovable, but there has to be room in this world for both - there certainly is in my heart.