I have been with Admiral (and its sister companies) for a few years.
No they don't like to insure cars with MODs, but they are by far the cheapest insurer (at least for me) beating all other quotes by over 100 GBP.
I have on one occasion had to make a claim and they were very good dealing with it.
Never found them shirty at all.
I do go around every year and get new quotes come insurance time, but other Co's always want to go way OTT both on the quote and Excess.
It has stopped me getting an SC, but TBH if you want the power get an IS300, and save money on the insurance.