only the problem i have bitcoin is that sometime it gets confirmation late. I know its not a fault of miners too but its annoying to sit back and wait for the confirmation to come.
The confirmation can take even longer than 1 hour sometimes.
When there are some stress test or simple attacks, it may take up to 2 days.
By this the funds are sent back to the sender and you should make again the tranasctions.
1.5hours is the longest I have waited. As long as you pay 0.1MBTC/KB fee, you will be fine with most stress test. It is expensive to execute higher fees ones. The transaction simply gets dropped out of the mempool and you can craft another transaction.
For me, the confirmations time, I hope Bitcoin adopt VNL Zero time confirmation..
It isn't too much of a risk to take for merchants in brick and mortar stores. Most only requires you to wait for a few seconds as it is impractical to make a double spend then. For online purchases, it isn't too time critical so 1-3 confirmations is reasonable.