I thought the part at the very end was unnecessary, but I didn't think it detracted much from everything up to that point. I do think that the main thing a series finale is supposed to do is provide a satisfying conclusion to what came before rather than to show off / get creative, but then I think the finale did that in general.
Overall, I thought it was great, one of the best episodes of the series, and did basically everything I would have wanted: happy ending for all of them, one last great Jane action scene, zip hallucination/memory stuff, bringing their time at the FBI to an end, sentimentality, tying everything together, lots of cameos...they even included Avery, and I was half convinced that post-Season 3 they were pretending she never existed. My only (minor) criticisms that I can think of that even bear mentioning were the very ending and the new FBI team being clear expys of the old ones. Awesome finale, even more awesome show.