Ace is a decent company to work for, but there are a few things to know before you get in.
1) This is hardball IFR/VFR in places like the Aleutian Chain and Southeast Alaska. It's great experience, and you will learn a ton, but it comes with a lot of challenges, and is higher risk.
2) In the summer the company has so much business, they can't take it all. Don't be surprised if most of your work days are 12-14 hours, and you're flying 120-130 hours a month. Great for the bank account and logbook, but very draining. On top of that, you're basically the bush Alaska version of a UPS truck driver, so expect to spend lots of time loading and unloading the 1900. It's really not bad, you just have to understand this is also a physical labor job too, and don't complain about it.
3) ACE is perpetually short on pilots, they're constantly in the process of hiring and upgrading guys. This means that schedules are very fluid, so don't take any of the 5 on 2 off stuff too literally. Don't be surprised if you work 9 on, 2 off, 7 on, 3 off, 11 on, 4 off, etc. Since lots of their mail flight have a 1 or 2 AM showtime, don't expect to have a good sleep rhythm.
4) Robbie, the chief pilot is good about upgrading people who are ready, but just understand you will by flying with low time captains in challenging conditions. This isn't a legacy airline with captains in their 50's and 60's with 25k hours. Most of the captains are 25-30, and in the 2k-3k range. They're eager to work, and do a good job, but realize that you will both be put in difficult, dangerous situations, and the guy in charge may not be much more experienced than you.
Overall, it's a great experience. It's rough with the schedule and the labor, but if you work hard, keep a good attitude, be humble and ask questions, you'll do fine. Adventure of a lifetime.