Sure, sometimes I miss things. For example, sometimes I miss how informal and undivided the relationship was between laity and leaders. The pastor at my Protestant church used to play basketball and do all sorts of things with us. He was just another one of the guys. There are negatives to that, but sometimes I miss that. And speaking of basketball, where am I supposed to play sports in an Orthodox Church? I've never seen a rec hall in one. It was a nice way to raise the awareness about Christianity without being pushy. You just invite a few friends to play some sport or other at the Church, and they could then decide for themselves whether they wanted to explore the other areas of the Church--though preferrably more than just the fellowship hall when we had food!
And I miss the music to some extent. It wasn't nearly as theologically orthodox as Orthodox music, but on an emotional level I could connect more. Some people talk about how an Orthodox liturgy is "like heaven" for them. Not for me. I've never been as comfortable in liturgical worship as I was in a contemporary worship service in a small church, with a guitar, maybe a piano, and the entire congregation singing. Not that I haven't found parts of liturgical worship that resonate with me, such as the joyful solemnity, and the historicity of liturgical worship appeals to the egghead in me. But, you know, when I went to a Protestant college we would have Bible studies, and it'd just be a dozen guys and a couple acoustic guitars singing contemporary worship songs, and those were some of the most heartfelt musical moments--or for that matter, religious experiences--I've had.
Usually the feelings pass. I wouldn't denigrate any of those things I just mentioned. I've moved on to other things, yes, but those former things had value. They just aren't for me at this point in my spritual walk. When I have those thoughts or feelings, I don't try to fight them--I mean, as long as they aren't harmful I don't fight them. Just like I sometimes recall memories of childhood, and that's fine, so to with religious memories. As long as they aren't harming you in some way, I don't think it's an issue. I don't think these types of memories or feelings are silly, I think they're perfectly natural for most of us. This is especially true if something we associate with a past church/experience is triggered by a song, a book or Bible, or whatever else. I think a priest would probably be able to advise you best, but I wouldn't sweat having feelings or memories concerning Presbyterianism or even sola scriptura. Just don't overreact, don't get all triumphalistic and prideful about Orthodoxy, and on the other hand don't let doubt take hold of you so that you start wanting to go back to where you were before. I know, even if true, it's easier said than done.