You may encounter the following issues:
Common misconception – Once a bitcoin transaction is seen by the recipient, it is irreversible.
Problem- A user can ‘undo’ a transaction by sending another transaction from the same account with a higher miners fee, ensuring the latter is accepted into a block first. See Video below
Solution – Wait for at least one confirmation to confirm double spend is unlikely. Wait for 6 conformations to rely on transaction being irreversible. (Cost to reverse transaction increases exponentially with each confirmation). Use payment channels (21.inc) or sidechains (lightning network) to have real time payment.
Long Confirmation Time
Common misconception – Blocks should confirm on average every 10 minutes, therefore any transaction will confirm in about 10 minutes.
Problem – This relies on suitable mining fees being included. Blocks are limited in size, and will accept as many transactions as can fit in a block (currently 1MB) starting with the highest $/byte for each transaction and working down the list of transactions in the mempool. Sometimes your transaction can fail to make it into the block due to a low mining fee, resulting in long confirmation times.
Solution – If your transaction has a suitable (~$0.10 as of 09/2016) mining fee your transaction will be included in the next block. If your transaction has too low a mining fee your transaction may not make it into the next block. If this happens you can either wait until a benevolent mining pool includes your low $/byte transaction or resend your transaction with a higher fee (email@example.com for help). Mining fees should be set to a suitable level automatically in most bitcoin wallets (including airbitz, electrum & jaxx). To determine fee yourself visit 21 inc’s calculator at bitcoinfees.21.co. In the long run the block size may have to be increased in order to increase the capacity of the network and reduce fees per transaction.