By the looks of it now it feels like gear second is no the same gear second as it was before timeskip.
Then it added to both speed and strength of Luffy making him suffer a lot.
Right now it seems it doesnt add that much to Luffys strength but it rather purely speeds him up not tiring him visibly as much as he used it till now.
I like concept of gear fourth and in last 2 days I gotten used to looks of it.
Seeing how strong Luffys attacks get while he is using it puts into different perspective many events that we seen till now - like Jinbei mocking Luffy for "results of his training" not being impressive and Luffys general attitude of feeling like he can take on anybody now. I find it quite awesome thing.
It makes me wonder if Luffy shrinks after using Gear 4th as he was shrinking after using Gear3rd before timeskip.
- now it feels like Sabo is the one that needs to catch up to Luffy(though maybe we didnt seen enough of Sabos power to say so).