I have both! The 5000 and the 2000. You wouldn't think the slight weight difference would be noticeable; but it is!
The 2000 is easier to 'throw around'; moving from cut to cut.
I probably shouldn't be writing a review yet; as these are just first impressions; after having used the 5000 for a while.
Like I said in the title; it's like cutting air. I was just getting started, or so I thought; on a 12" piece of Locust. Before I could get comfortable the saw was through the wood!
As for runtime and/or overheating; I can't speak to that; not having used it enough yet. But so far; I really like it; and I would buy it again.