Definitely a different feeling to the SPDs. I had SLs first and then got a set of SPDs for my fixie. At first, I thought they were awfully difficult to operate compared to my SLs and it took a few weeks before it felt natural to clip in this way. I suspect the fixed wheel element didn't help me there, either.

My point is the same as posted by someone above: muscle memory and experience with the system is the key to smooth engagements every time. The other issues you describe (noise from the stability plate) I cannot comment on as neither of my sets of Ultegra pedals have made any noise. One for the LBS to check, if you're unsure.

Hope that helps.