Had this about a week. I'm not a pro, I only tinker about at home and this is ideal. It could mean that you don't need an amp for your guitar, saving money and space! My PC just has on-board sound, but a decent sub and speakers and the sound is brilliant with no lag. The software is good giving access to 3 different amp packages but only 1 can be registered the other 2 are 30 day trials but great for the money.

I bought this device because I was going on a trip and I wanted to play my electric guitar without carrying an amplifier with me. I'm using it with my Apple Macbook (core 2 Duo) and Amplitube 2 and there is no latency at all. Easy to set up (no drivers for Macs) and I can monitor the clean sound through the device or the processed sound through my speakers. I haven't installed the software that came with it because I have other similar software.
My only problem is that the sound is not as good as when running your guitar through an amp. It's a bit artificial and it has less sustain. Other than that, it's a great device