Unlike the anime or manga, PGSM focuses more on the civilian lives of the Sailor Soldiers than previous versions do. While fighting as soldiers, there is a stronger emphasis on the past lives of all the sailors, and a sense of a burden with it more so than other versions.
Another major change is the back-story behind Sailor Venus. Rather than being an ordinary girl, Aino Minako is a famous idol in addition to fighting as Sailor V. Her personality is also tweaked, and she steps into the role of the leader of the senshi a bit more along with a strong lone-wolf streak.
The show also introduces new aspects of characters, such as Sailor Luna, Dark Mercury, and whole new depths to the Shittenou. Some things that the manga or anime hinted at are explored in depth in this show as well, including the past life dynamic between Endymion and the Shittenou. Another new character is Beryl's shadow, Kuroki Mio.
The series has a very strong storyline that gets you addicted fairly quickly. While at first it feels very similar to either the manga or anime version, it quickly branches off in a new direction (about the time Sailor Jupiter is introduced).
Special effects were surprisingly decent given the time (they are already out-dated by today's standards, of course) and the small budget for a children's show. The attacks are surprisingly believable, and the transformations are all pretty decent (of those, in my opinion Sailormoon's transformation scene is the worst...)
The acting is very well done, and the actresses and actors do a great job with their given parts. The Shittenou all have distinct personalities and styles, the Sailor Senshi all manage to play their roles quite nicely as well- a standout is the performance of Kitagawa Keiko (Rei), who played a very manga version of Rei and did a spectacular job walking the line between independent and mean.
The monsters of the day are fairly laughable. The style is very Power Rangers and sometimes it's hard to be worried about them running around the city draining energy... they don't look very capable.
The fight scenes, aside from the actual attack sequences, are kind of silly. There is very little hitting and punching, more or less there is kind of dancing and a bit of acrobatics, but a lot of time I have to wonder what exactly a cartwheel is going to do to help in battle- except maybe confuse the enemy.
PGSM isn't for everyone, and it can be a bit hard to get into if you don't have an open mind. However, it is definitely worth the first few episodes to get into the new story lines. Once you're there, the show is addicting and will keep you watching just to find out what happens next.