Scalability,Cybersecurity issues,Price volatility and lack of inherent value,Regulations.
1. Scalability is not an issue with most altcoins as they have quicker blocks and higher blocksize.
2. Security of your crypto is up to you. Simply a strong password will protect you everywhere.
3. Being volatile should be considered as an advantage rather than considering as a disadvantage as all traders and investors love it. You need to be skilled to fish here.
4. Inheriting your cryptos to your decedents if your basic responsibility. Same as any other digital things.
5. Regulation is something we must expect. Still cryptos are created for privacy and freedom. So, we need to build a system to regulate ourselves in way the true concepts of cryptos will not be disturbed.
Fast and Inexpensive
All electronic payment systems are faster.
Being inexpensive is something we must consider as a biggest advantage of cryptos. But, due to scalability issues we have issues on this advantages and I guess it will be resolved as early as possible.
Decentralized issuance, Lower fraud risks and Transparency...
These are unique advantages of cryptocurrencies that we could enjoy and we need to remember these are beyond imagination for a financial system till bitcoin arrived. So, overall cryptos are having more advantages than disadvantages.