05-09-2016, 10:21 PM
You can't mine any BTC yourself with a GPU. That fun ended a few years ago. I no longer heat my house during winter with GPUs...
You can mine some alt-coins with GPUs still, however unless you already own a GPU and just want to play around it's not worth doing. There are specialized chips for mining however you're competing worldwide against people with low cost electric and direct access to the chips. I would not advice any new comer to get into that game as it's so very easy to lose money.
The official BTC puzzle create code is hack proof, the algorithm to determine who mines the coin is too random to crack. At least it's stood up for the history of BTC.
Transaction time has been a bit of an issue at times, this may be solved shortly. Some new updates to the bitcoin-core software will be released shortly. As there is no central authority so it takes the community as a whole to decide, depending on how many people start using things.
MT Gox was scammed from the inside. No different than a Bernie Madoff situation really. Don't leave all of your coins on exchanges unless you're trading. With that said exchanges have been rather safer lately yet I still wouldn't keep all of your coins there unless you have a need to.