We used them for a film festival I helped run almost 10 years ago now. We were a pretty shoestring operation at the time and needed to get our cut of the money from the first few days' sales to fund an event at the end of the festival (whee!) and they were quite helpful in transferring it to us in an expedited manner.

I don't know how they are now, but they were great to work with then.

I always cheer for competitors and I used Brown Paper Tickets a couple times now without issue, but in my experience, the alternatives tend to crumble under the pressure when they try selling tickets for a truly high-demand show (usually when a high-profile act plays a venue much smaller than they usually do). For all its sins, Ticketmaster does seem to manage to handle high loads on a regular basis.

There is also TicketLeap https://www.ticketleap.com/

There are plenty of start ups in this space I just don't believe any of them can get exclusive deals with the main huge venues that are part owned by Ticketmaster's parent company.

I've had to use them a couple times at a local gallery that I like, and I like their general idea but that site needs a lot of work.