This really isn't that fantastic of a deal.
I would say the "average" road warrior is doing a roughly 3 weeks on/1 week off schedule. Spending every 4th week with minimal travel. Some weeks you'll do a multi-city trip (eg: Boston to Charlotte on Monday, Charlotte to Miami Wednesday, Miami back to Boston Friday), but more commonly it's a 4 day 1-city trip (Boston to Miami on Monday, Miami to Boston Friday morning).
Regional flights (their $1500 option) can easily be found for $200-$400 roundtrip with even minimal effort. Larger corporations typically make you book through a travel department which pretty much forces you into the cheaper options anyway. Thus the $1500 option is really only a moderate deal if you average 4 weeks/month of travel AND have at least 1 multi-leg flight per month.
The 7-day advance booking requirement really cramps the value proposition. I'd say 75% of my flights are booked less than 7 days in advance. Many times the meeting is scheduled 2 or 3 weeks in advance, but last-minute cancellations are common because a big job comes up for an integrator and they need to re-schedule our meeting so they can go out and do a demo at a customer site, or respond to an RFP, etc.
Overall, these don't look like terrible deals, but I would wager the typical traveller would lose money on this long-term relative to booking individual flights as and when needed. It's also unclear if you can always choose your preferred airline, which if you can't it makes it harder to build status with a given carrier. If you're a truly frequent traveller, then you know that it's not worth it long-term bouncing between 2 or 3 carriers where you never get status just to save $500/year on travel expense.