To start, I love this game. If you haven't checked it out please do so. It's now free to download from Abandonia.
I've read countless reviews for Sid Meier's Covert Action, all with the common theme. They reference what they call is the "Covert Action" effect. They claim that this game is a perfect example of how many different gameplay concepts put together can sometimes lower the overall enjoyability factor.
I disagree.
Many older style games generally start off hard and intense, then quickly get harder and intensify, up until the point where you can't keep up. The change in pace is refreshing and is a common mechanic used in modern games, providing periods of intense action mixed with slower paced gameplay and the slowest of gameplay (cutscenes!).
I like Covert Action for keeping a balance in the tempo with the mixture of action (the combat and driving games) with slower paced thought pieces (phone tapping, decrypting etc). On top of this, I like how the game encourages you to keep notes by throwing clue after clue at you, to the point where you really need to be writing down names of interest to make sure you can find out as much as possible during every break in.
Overall I can understand why this game isn't for everyone, but if you are a spy nut (like me!) then definitely give this a go. It's made easy with great software like DOSBox.