Being that we're only about 45 min from EWR, a Continental hub, we've flown them almost exclusively for about 15 yrs now. When we weren't flying CO we were on UA (usually for destinations CO didn't serve, or UA had more choices). We also use CO & UA credit cards for just about everything and between travel and the card we end up with lots of miles. UA has always been mediocre with using the miles, but with CO it used to be that we would buy a cheap fare... like under $300pp rt... and use miles to upgrade. Since the merger the fees to use miles to upgrade are insane to most destinations. When I've checked it seems like the fee can be half or more of the fare. Insane. And of course it's gotten a lot harder to get the saver miles (30K each way for first/business). With the UA "economy plus" being adopted into this new airline it also cut out a good chunk of economy seats on many flights. The upgrade to those seats for the 5" more legroom varies too. I've seen anywhere from $15 to $75, depending on the flights.
Overall, they took everything good from CO and replaced it with everything that stunk from UA. Charges for everything, higher fares, harder to use miles, etc., etc.
Definitely sticker shock fare shopping for CZM or CUN, or anywhere in the Caribbean these days. The occasional times we had to pay $400-425 I used to complain. No it looks like $600+ is going to be the norm. It's going to be a lot of time wasted ticket shopping, playing with dates, times, connections, etc., to get reasonable fares. I'm just glad we usually have some flexibility and aren't held to any specific vacation days. The problem you run into shopping flights though is that if you don't book right when you see it, it might not be there when you go back even 10 minutes later. Ended up spending almost $100 more a person on a trip in Oct that way. Only 20 minutes and it was gone.