Pros
The Paid Time Off policy is probably the single greatest thing Unum has going. New employees get 23 days. Every 5 years, add 5 days to that up to a maximum of 33. You can also roll 5 days year-over-year, so the old-timers have 38 days! Career advancement is a little slow for young people today, but the workforce is exceptionally old, and Unum still has a strong pension plan. In the next 15 years there could be a pretty serious exodus to retirement, so the Gen Y'ers who get in now and learn the business will be very well positioned for the future. Also Chattanooga is a great city to live in if you like outdoor and athletic activity. The nightlife in Chattanooga is a little lacking, but is perfectly enjoyable if you like the tavern and pool-hall scene. Just don't expect to find long lines to get into clubs with bottle service.
Cons
Insurance is not an inherently thrilling industry. The workforce is pretty "seasoned" and most are just coasting, so the openings to move up aren't there yet. Still, see the good reasons above for more on this. As a younger person, I'm not a big fan of the retirement plan. Unum has DB pension, and a weak 401k match. I believe its 50% on up to 6%. I'd prefer a full match, plus vested 401k contributions, since you don't have to rely on the company to fund and invest its pension properly. Seems like a lot of companies are cutting or underfunding these. Several departments are bogged down by red tape, approval committees, and typical corporate bureaucracy. Good managers shield their employees from it, but some are just coasting to retirement and do absolutely nothing, which surprisingly is a pretty effective way to keep your job.