Are you trying to monetize this? Who is your target market? I'm genuinely curious.
I work at $BIGCORP in analytics with a lot of large excel spreadsheets every day. If I bump up against row limits or need functionality not available in excel I'll import into a corporate oracle db and manipulate it with SQL. A lot of the people that I collaborate with can only use Excel and it's often faster to just manipulate data there rather than put it into a real db or parse it with another tool.
With modern computers I can tell you it is a very rare occurrence that I cause excel to choke. On the order of once a quarter.