The problem with not having many issues yet is that it's difficult to find much to say about them. But one thing I have been noticing is the change in cover styles Tammy went through.
The early issues have a fairly generic composition, although the style places it firmly in the early 1970's, with its sub-psychodelia influences. It's colourful but bland, inevitably showing a generic girl in the foreground and a simply realised scene behind her. It makes me think of a posed photo, only redrawn in a simplified paint-by-numbers style.
Then at some point we get a change of direction, and by 1975 we have two cover girls, who appear regularly, often doing some Tammy-related activity. These covers often have some comedic element, or even meta-commentary. The odd thing, though, is the way their hair changes colour. Generally the short one with bunches is blonde, and the taller one with shoulder length hair is a brunette, but sometimes one of them is a very orangey redhead, and occasionally their hair colouring is completely reversed. I'm told they even had a story entitled The Cover Girls in one issue, but I don't have that one yet.
I believe they are supposed to represent Tammy and one of the various comics that Tammy swallowed up, but I'm not sure which one.
Then there's a period where they have a story starting on the cover. I don't know much about that as I don't have any examples from that era yet.
The Final cover style that took over in the last couple of years, along with a new title logo, was a fairly straightforward spotlighting of one of the features in the comic, often the popular Bela Barlow. I can't help feeling that the comic loses some of its warmth and individuality with the passing of the Cover Girls. Instead of giving you a fun little scene with the comic-obsessed duo, it's just an advert, sometimes even reusing art from inside the comic. Even the logo has gone rather bland.