I didn't live in Polden myself, but from what I've been told, it is really nice and modern accommodation but it isn't that social in comparison with other accommodations. This is mainly because it is also accommodation for postgraduates, who tend to prefer quieter accommodation, and it is on the far west side of campus so it is less central. It is also more expensive than other more sociable but less modern ensuite halls such as Woodland and Marlborough/Solsbury. Overall, it is really lovely accommodation but it is more suitable a) if it is within your budget and b) if you would prefer slightly quieter halls.
I hope this helps,
Jessica, a final year NatSci student