With the forecast for the weekend, I expect it to be mobbed.
As to value, depends on where you're coming from. My wife was at it last year and wasn't too impressed, but then she was at RHS Chelsea earlier, so she may have been judging it against a ridiculously high standard. She's more into plants than people selling decking and barbecues.
They were talking to one of the backers/sponsors on Morning Ireland this morning and I thought the prices mentioned were on the high side, e.g. (IIRC) €20 per adult.