It's been several weeks now that I have had the Mylo and I have a few things to add.
First, the new firmware upgrade that installs the Tmobile Hotspot support is great. When you get near a Tmobile Hot Spot and the Wi-Fi is on, the device logs you in quickly with no username or password. I was using my cell phone at the Starbucks near Sand Hill Road and the reception was terrible. I grabbed the Mylo and called out to the person I was talking to and it was crystal clear.
There are two things on the Mylo that didn't jump out at me at first that I think are worth noting. First, the Wi-Fi sucks an unbelievable amount of juice. It's almost like you can watch the battery drain while Wi-Fi is on. That has to get fixed. I doubt that I could leave a fully charged device on Wifi on all day.
The other item is media handling. I am pretty bummed that the only way to get content to the device is through the USB port and the PC software. I assumed that I could take MP4 video on my Sony Camcorder and pop it into the Mylo and play it back. Nope. It has to go through some strange conversion. Download an MP3? Nope. The PSP came up with improved support over time. I hope that this is on the roadmap. There may be a reason why they set it up this way but it only seems like a barrier to me.