Upon watching it again, I think it was probably the worst of the 'big' show finales. Which is no great damning or anything. But it's the one that ended the most like a regular TV show. The Sopranos, The Wire, and even The Shield if you want to include it, all ended on a far more powerful sense of their own terms.
On reflection they probably shouldn't have done the flashforwards. Walt's 'fall' would've been far more powerful had we not already known it was heading that way, and they wouldn't have been hamstrung by the introduction of the big feck off gun (which I agree, does seem a very weird thing to include blind) Also the Lydia/ricin plot just felt more like a "we need to do something with the ricin now" scene than anything the show was organically heading towards, or indeed anything we needed or even wanted to see. Lydia's in the episode more than Jesse FFS and is the last person Walt talks to. Lydia? Really? Who gives a feck?
Still a magnificent show, but yeah, watching the finale again, it was good, but not great. In the writing at least. The production, acting etc was all brilliant.