Full disclosure: Rainier is one of my main sponsors. Its possible that you may have seen the video that I did for them about the RUC. But that being said when I received the rifle I was EXTREMELY impressed with it. You wont be disappointed. Like APL-G35 said the fit and finish is excellent, and the gun is way more accurate than something at that price-point should be.
I shot a 1/2moa group in the video at 100 yards, and I have done better with it at times, at longer distances. I think with a trigger upgrade like you are planning, you aren't going to want for anything else. When I originally received it I shot a 3 shot group to get an idea of what sort of scope adjustments I needed to make and thought something was wrong when I could only see one hole through my spotting scope. Then I realized that first 3 shots out of the rifle were all in the same hole. Those were my reloads (and not my precision ammo, just 55grain hoser stuff). If you end up with one, let me know, and I can get you the load data for what it likes.
I have spent quite a bit of time with the one I have, so if you have any questions, feel free to ask away!
Chris