Hi Alen,
This tool essentially is meant for comparing publisher and subscriber tables (http://msdn.microsoft.com/en-us/library/ms162843.aspx). I've tried this tool to compare tables with about 25 million records on pretty standard server (Quad core + 4GB RAM, on VM) and it took about 15 minutes. This test I did was on same VM machine, same instance but different DBs.
HTH!
Cheers,
- Harish