Seeing an active volcano in eruption so close is really impressive! But first we had to hike quite a bit. We are not super experienced hikers, but we do hike in the mountains about once a month and, although this hike was not terribly hard, I can't call it easy neither. If you do it, make sure you are well-prepared. First of all, you need real hiking boots. I personally often hike without them, so believe me, you really need them for this hike. We rented ours together with flashlights (without which it is impossible to go down) for 9 EUR per person in the shop on the Church square (and since we were leaving early next morning before the shop opened, we just left them in Magmatrek office after the hike). Magmatrek also provided us with walking sticks (at no extra cost) and there wasn't a minute during the hike when I wasn't feeling happy about having it! Another thing you will absolutely need is water, and people are not exaggerating about 2 L per person (at least in summer)! We had only 3 L for the two of us and it was barely enough (and I am pretty sure, my boyfriend was pretending not to be thirsty, so that I could have more). It was very hot during the first hours of the hike and everyone had their t-shirts completely wet with sweat. So it is better to take a least one (ideally even two ) clean t-shirt to change, as well as a warm jacket, because when you are finally at the top and the sun goes down, it gets very windy and cold there. We were both pretty tired and starving (yes, food, don't forget food!) by the time we arrived to the top, but the time we spent there sitting on the warm ground, watching first the sunset then the volcano was great, absolutely worth the hike! Going down afterward is rather easy - most of the time you just slide down the black sand.
As to the company, we were happy with Magmatrek - they answered our emails rapidly, made sure that everyone had all the necessary things for the hike, advanced at a reasonable speed (stops every 20-30 min, most stops were short, but when you hike, pausing for a long time will only make it more difficult) and provided interesting information about volcano and the island.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.