The danger of unicameral systems is that they can be dominated by a powerful individual/s and can be very unaccountable unless a lot of checks and balances are in place (remember Henry McLeish and Jack McConnell too). Scotland has a "ministerial code" but if the mechanism that enforces it becomes corrupted or the enforcement mechanism is weak and unclear then the dangers are obvious.
So devolution created a government with an array of law-making powers but lost most of the checks and balances in the British Constitution.
These are other countries which have a unicameral legislature. Apart from the Scandinavian countries, they're not exactly shining beacons of accountable democracy at work. Its also interesting that Switzerland, an even smaller country than Scotland, has a highly accountable bicameral system.
Albania, Andorra, Azerbijan, Angola, Armenia, Bangladesh, Benin, Botswana, Brunei, Burkina Faso, Central African Republic, Chad, China, Costa Rica, Croatia, Cuba, Cyprus, Denmark, Djibouti, Ecuador, Egypt, El Salvador, Eritrea, Estonia, Fiji, Finland, Gambia, Estonia, Greece, Guatemala, Guyana, Honduras, Hungary, Iceland, Iran, Iraq, Israel, North Korea, South Korea, Kuwait, Krygystan, Laos, Latvia, Lebanon, Libya, Lithuania, Malawi, Moldova, Mongolia, Montenegro, Mozambique, New Zealand, Nicaragua, Niger, North Macedonia, Norway, Palestine, Panama, Papua New Guinea, Peru, Portugal, Quatar, Senegal, Serbia, Sierra Leone, Singapore, Slovakia, Sri Lanka, Surinam, Sweden, Syria, Tanzania, Tunisia, Turkey, Turkmenistan, Uganda, Ukraine, United Araba Emirates, Venezuela, Vietnam, Zambia.