My biggest problems with Bitcoins is if fluctuation of the price comes.
and then sometimes my transaction is extremely delayed before my confirmation
comes in into my email

If you are trading bitcoin then price fluctuation should not be a problem for you, as I trade bitcoin and I take best advantage of each and every fluctuation to make profits from it.
This fluctuations are good for traders. You can take advantage of it being low. Buying some before the price climbs up again and selling when it begins to drop. With the current rate going, holding on to what you have may be beneficial
Yes for trade Bitcoin price fluctuation is good. If it fluctuates means you can trade easily or else how can we trade. If the price is stable how can we trade? So price fluctuation is not a problem for traders. But if you are gambler then it is an issue for you. Because players can sell their bitcoins whenever they money so in that time price is cheap means it will hurt them.
Something i like to confirm is the transactions made before bitcoin reach the 600 dollars, when it were at 400 , i had see a payment from megatypers, from 1,50 dollars worthing around 5 dollars nowadays soo, this for sure its interesting. For other side i had spent more bitcoins before they i would use now . The biggest problem is how to earn bitcoin , and be able to hold them, this year is frustating all invested or losted to scammers.
for merchand, fluctuation rate is very bad, if the merchand accept bitcoin when the price $700, then the 2nd day price of bitcoin fail to $500, the merchand will lose $200, but if the price of bitcoin rise in fluctuation rate, the merchand will get some profit just with accept bitcoin.