I have such a love/hate relationship with the Evans calftone heads. I used them exclusively for something like 2 years on three different kits during self practice, band rehearsals, recording, and live performance so I've got a good amount of experience with them.
The good:
They look really super cool (I know sound is more important but if you aren't into the look it will always bug you). They are very easy to tune and accept high, medium, and low tunings equally well. They have a fantastic bop tone when tuned high and a great classic rock/country/'vintage' sound in the low and medium tunings. They have a natural warmth and fatness that I've found with no other head. They are absolutely the perfect middle ground between the open tone of a single ply head and the overtone reduction of a two ply head. They work equally well as both batter and resonant heads, work great in unison on both sides of the drum, and work impressively well on concert toms. They are super punchy and warm bass drum heads, especially if you don't use pillows/additional muffling. Their sound with brushes is pleasing but very 'pre broken in'. They don't have the plastic 'bonk' that most heads do (regardless of coated vs non coated or company who makes them, I hate the plastic 'bonk' of most heads).
The bad:
The durability is horrendous. I'm not a heavy player at all and use 7a sticks but I found myself replacing snare heads every few weeks and tom heads every few months, by contrast a standard single ply coated head lasts me 6+ months on the snare and 12+ months on toms and I never break sticks. They are only 7mil thick (amb or g1 is 10mil for example) and extremely prone to denting and 'dishing' in the middle. I've had brand new heads on a snare last as short as two rehearsals before denting and 'dishing' (again a G1 would last me 6+ months by example). Even if you are lucky enough to not dent them right away... The coating will bubble. Noticably. What starts off as a small annoying wrinkle you see quickly turns into a soft mushy spot that pushes around as you play so it feels like you are playing on the 'dead' (foam) side of a practice pad. They are very very quiet, a low tuned hydraulic has more volume (less tone but more volume). The brush sound is very subtle which can be good or bad depending on preference.
To sum it up, I love these heads but got really tired of replacing them bi-monthly. I've since moved on the the UV1, not the same tone but friggin bullet proof.
Hope that helps!
PS: if you do try them, spring for a full tom pack and not just a single head that way you can get a realistic feel out of them. You can spend $45+ on 2 single heads or $35-$40 for a 3 head tom pack, no brainier.