I took some classes this spring, and they had a HQ Fusion and the new Infinity set up. The classes were on long arm quilting, and not specifically about the machines. I own a Fusion (owned a Bailey before it) but have not used it all that much so far.
The Infinity was a lot noisier (and I do mean A LOT). and seemed pickier about things. And when it ran out of bobbin thread, the instructor had to hunt down a bottle of compressed air and casually said that you need compressed air to adequately clean the bobbin area.
The Infinity is enough different than the earlier HQ machine (Sweet 16, Avante, Fushion) that I would not take recommendations from users of those for the Infinity, as it is too different. There was nothing about the Infinity that made me wish I had it instead of the Fusion - but I also don't use the computer and maybe that is a big advantage. I don't think anyone in the class of 25 (all long arm owners) were really impressed with the Infinity over what they currently owned - however the noise really did turn a lot of people off.
This really is not a "review" - only suggesting that you should talk to Infinity owners about the specific machine as it's not just a longer Fusion (which is basically a longer Avante from what I saw when I was looking at both).