I took Bhat and didn't have any problems spending it. I've been to Turkey with Lira which was a pain at times as it seems they much prefer pounds, dollars or euros. In Thailand I didn't get any mention of any currency other than Bhat and that was in both small villages and big cities.
Same here. I spent a month in Thailand and used Bhat for everything. My dad moved over there and uses Bhat too. Never seen any point/benefit in taking pounds/dollars there.