I agree the TM2 is very top heavy. It has an annoying tenancy to fall over if you push the screen past 90 degrees. I haven't had any problems with the battery myself (haven't accidentally unlatched it and I don't use it as a handle given the curved, smallish design).
In our review, we have a fix for the touch screen going to sleep via power savings and that might help with the perceived lag. To fix this, right-click on the My Computer icon on the desktop. Then select the Device Manager link. Expand the HID devices listing and select the first USB input device (you'll find it low down in the HID devices list). Double-click on it and change the power settings via the power managment tab. Uncheck the "turn off this device to save power" option. Now the touch screen won't keep going to sleep. Has worked on mine for the several months I've owned it.
The EMR pen works the same way on every Windows tablet PC since they first shipped in 2002. My Wacom Intuos tablet also works the same way. IT is not unique to HP or the TM2. The digitizer detects the EMR pen up to an inch away. Some folks actually find this useful (no need to touch the screen since you can hover). But it's obviously not the way pen and paper work so it can feel awkward until you become accustomed to it.