I have been using the ESV Study Bible on my mobile device (Palm TX) over the internet and it has been working really great. It does not use frames, and has it all in a single colum with hyper-links (I don’t know if it is my browser that reformats it or not?). It works really well. Although I am not very comfortable reading long term on such a small device, but none the less it is really cool to be able to have the full study notes of the ESVSB on my device.
Again, this only works if I am connected on the internet, so it is limited for me since my device only supports WiFi. If you have another device like iPhone, or something then obviously you would have interent access all the time.