I've flown about 15 segments on copa in the past year, all of them upgrades to business.

For me the pros are:
1. Really efficient operation in pty
2. Full eqms and bonuses with ua
3. Cheap fares
4. Upgrades that clear! I was on a flight pty-gru last week with the p.s. style seats where the cabin was willed 2/16!
5. Rum of the month...usually Flor de Caņa 18, which is might tasty.
6. Very gracious in flight service. Have yet to come across a fa with an attitude.

Cons:
1. Food in business is the worst I've seen on any airline. I honestly think that sometimes it is the economy food put on plates. Portions are small.
2. Spotty Ife. They usually have on demand for the Brasil flights, but that's it.
3. No showers in the lounge in pty. many of the flights operated by cm are longer than short flights to Europe, and when you factor in that you could fly as far as mvd-lax with them, the lack of a shower becomes important. Even tam has a shower in its business lounge...