Positive: Bitcoin gets more publicity, the market gets more volume which is always a good thing
Negative: when most users are investors, it's easier to take over Bitcoin. Imagine government saying that either Bitcoin protocol will have to change or it will get banned. Most investors will support this fork because it will protect their investment at least in short term, so the majority of PoW and money will be on the side of the fork, and true Bitcoiners will be left in the minority. They will keep calling the original chain Bitcoin, but for the rest of the world the new chain will be Bitcoin.
Temporary volume is not good I do not think for the survival of Bitcoin and does not help us in the long term. I do not think increased volume atm has any positive effect. The negatives of people buying in Bitcoin and then selling at a later date for fiat are more prominent then the pros. The pros are that a lot of people have made a huge amount of money because of the swings in price difference and more and more people are hearing about Bitcoin which makes these swings more common but when that stops Bitcoin needs to be used as a currency because these swings will not happen as often as they do now. The problem I see with that is when this does happen Bitcoin has issues with fees and not a lot of merchants accepting it and the value could take a big hit because of these reasons.