My current and previous NXs have both been insured with Lexus Motor Insurance. I have found them to be quite competitive on price, i.e. matching, or in some cases, being lower than the quotes I received from the usual suspects or the comparison websites (for similar cover; excess; etc.).
Thankfully I haven't had the chance to see how well they respond to a claim yet (famous last words!) but am hopeful that it will be a trouble-free experience. Their promise of authorising repairs at Lexus approved body-shops using genuine Lexus parts is a major plus for me. Also, being associated with the Lexus "brand" must help surely - or am I being naive?
Having said that - if their prices were well over what other insurers were quoting, would I still go with them? Probably not.
I would say however that their customer service when renewing or changing cars in the past has been a little underwhelming. For example my recent renewal quote had my marital status wrong (when it was correct in the previous year) plus they only record you as having 10 years NCB even if you have actually accumulated more (so not sure how that will work if I choose to go somewhere else and need to provide proof of NCB). Hopefully their claims process is a little better. Like you, I'd be interested to hear what others have to say in that regard.