I actually agree with a couple of you here. Transformer by itself was coming close to the line of infringement, but IMO clearly not "sueable" because that's what the device does... it transforms from a tablet to a laptop, and "Transformer" is a common word.
Now the addition of "Prime", a less common word, to the second generation is IMO a violation. You are obviously trying to capitalize on the already existing name recognition that's already out there.
Sure you might want to go with a word other than just saying "Transformer 2". There is no style to that. So say you went with something like "Transformer Rebound" or "Transformer Platinum". Customers could easily be like "what was that new Transformer tablet called again? I don't know, Re-something..." But everyone knows of the connection between Transformers and Optimus Prime. There is no way your customers are going to forget that name, and when the name is unforgettable, there is a better likely hood that customers will try and find THAT product first when they start their buying process.
Sure, the Hasbro product of robots, and the Asus Tablet's really have nothing to do with each other and there is no "confusion" over "hey I thought I was buying a robot when I bought this tablet"... but there is a direct connection of the improved possibility of success of the tablet, because of the perceived LINK to the very successful Transformer product line by Hasbro.
And for that, Hasbro should get paid.