Definitely worth going. Shopping is reasonable and the XC has very good viewing especially on the hill behind the tradestands. ERM is on Sunday so should have a good line up.
I went to their festival of eventing a few years ago and it was a great day, just a bit far to go there and back in a day for me or I'd happily go back
It is good. Crowded, but there is lots to see and do with an arena programme all day, shopping, but not too much and very good viewing of the cross country course so you can sit and see a few fences, if not too wet.
Last time I went I watched the Shetland Grand National and they were surprising naughty. One refused to start and another carted the rider out of the ring!