Many people are a bit let down after their first dive on a rebreather because they are not used to diving the configuration (which is very different than OC), and they don't really get any of the major benefits.
Diving an Evolution in shallow water can be difficult because you may not be fully aware of when you are firing your ADV, and therefore you introduce diluent by accident. This will cause the solenoid to fire, which will change your bouyancy. For a rebreather to dive most comfortably, it should be dived at minimum counterlung volume, and the skill can't be perfected in 2 dives.
Also, I'm sure the unit was not set up perfectly for you. For example, the heavy mouthpiece can be made comfortable by adjusting the position of the hoses, or even cutting them shorter.
You really won't appreciate the full benefit of diving a Rebreather in shallow water either. The times when I love my unit the most are when doing multi-level dives within recreational limits, or deep dives. There is usually no way to carry enough ideal mixes when diving OC to be even close to a RB.
I recently had the opposite experience to yours...I did an OC dive!!!
I had a student who wanted to try out both of my units so that he could decide which one he wanted to buy, so rather than disinfecting both units before switching, I thought I'd just dive an aluminum 80. It was only a pool dive. I felt like the 2nd stage was jamming air into my mouth, and my bouyancy was nowhere near perfect. That was my first OC dive in over a year, and my second in the past 3 years. Hopefully it will be my last.
Aloha,
Charlie