It mentions using compression to basically decrease the data that is being sent and received, this could work as long as your system meets minimum system requirements.
What are the minimum system requirements for EarthLink Accelerator?
EarthLink Accelerator works with most Microsoft® WindowsTM-based personal computers in use today, including virtually all PCs purchased within the last four years.
Platforms
Windows 98/NT 4. 0/2000/Me/XP
Browsers
Microsoft Internet Explorer 5. 0 or later
Netscape 4. 7 or later
MSN Explorer
System Requirements
Available disk space—25MB (135MB recommended)
Total system memory (RAM)—32MB (64MB highly recommended)
The forst thing that comes to mind here is having other processes running and trying to run this, say you are playing an MP3 file and surfing the TDR at the same time, the processor may get into a pinch if it is an older model and perform both functions poorly.
A fast modem, a fast CPU and accelerator should work though, probably cheaper than DSL or cable, Good Luck!
JJ