We've been doing a trial with Reading Eggs after it was recommended to me. I was wondering what people think of this, I googled reviews and could only find old reviews. I feel like ds who is in year 1 and nearly 6 is really benefitting from the Reading Eggspress section. But dd in preschool, nearly 4, doesn't seem to be benefitting so much. She really enjoys it but it seemed odd that they start on words from the beginning. And there doesn't seem to be enough time on explaining blending which is where she is struggling.
what level did your DD start at? DS did the first 40 levels or so, which basically taught him the single letter graphemes but no long vowel sounds IIRC, and to blend. Blending took a little while - at first he never managed the exercises that required the ability to blend, but every level has some exercises focused on blending and eventually he got it.
You have to be aware that the programme is not systematic synthetic phonics, as is (supposed to be) taught in English schools, but rather, analytic phonics. That shows strongly from level 40 upwards. You will find that the programme introduces lots of 'topic words' that the child cannot decode yet, e.g. 'castle' - the child is then meant to 'read' the word by clues such as the first letter, the whole word shape, context, pictures... which is really bad practice, from a SSP perspective. Also, rather than continuing with the phonics teaching and covering e.g. digraphs/ long vowel sounds, the programme from level 40 upwards focuses on syllables. So IMO it is fine for the first 40 levels, but after that you significantly diverge from how phonics is taught at school and that can cause problems.
DS is now in Y1 like your DS, we never went back to Reading Eggs. He practises comprehension on readtheory.org which I find excellent, and is free, and is often recommended on here. But can't compare it to ReadingEggspress as we never did that.
We found reading eggs very slow, because it goes through pairs of letters at am an etc as separate lessons. Didn't try the express section though. Blending bit is tricky in games like that - once they get it they get it. So DS always complained there was too much of the blending stuff.
For preschool age, alphablocks and teach your monster to read are great and also free. And better in tune with UK teaching, tho I think some teachers might take issue with the 'tricky words' in tymtr.
We did a bit of reading eggs but like the others found it a bit slow and confusing on the blending. He did like some of it but I wasn't prepared to pay for a full year. We did Teach your Monster instead and can really recommend it. DS was a bit reluctant and struggled with straight reading but this really helped and he enjoyed the games and creating his monster.