This is a great game and technically an improvement over the first iteration. However, I do prefer the first game when it comes to gameplay.
Don't get me wrong, the armor suit controls fine and the platforming controls are superb. My main issue with this game is the difficulty curve.
The first stage was the most difficult in my experience, because you only start out with a maximum of 3 lives. However, this amount increases when you find secret rooms. These aren't very well hidden and I actually found 9 out of 10 secret area's on my first playthrough. So in the later stages, you can carry a lot of lives. It doesn't help either that the lives drop rate of enemies is high as well.
If the difficulty was higher it would have fixed my second complaint as well. It took me around 3,5 hours to finish it. The first game took me around 5 hours to finish, probably because it was more difficult.
Those are my only two complaints. Everything else is very impressive and a must play for every C64 (Mini) owner.