Just as an update to my previous posts in this thread:
I did in fact have .Net Framework 4.5.2 installed when I reported the sluggishness problem. However, I can report that the "problem" completely went away, even in the BETA version, within about 24 hrs. It wasn't because I toggled Implicit Auto Completion to off - it was something else. It could even have been some kind of background updates happening on my machine from something else. Anyway, problem is no longer. BETA worked great, and release v5.00 is also excellent! Thanks for the responses.