Sphinx has so much potential, you can't even imagine.
I plan to do all heavy queries through Sphinx... for example the latest threads.
My new project will be similar to digg.com and will be 60% powered by Sphinx. I'm in the process of buying 4 servers (dual quad core 5410, 8Gb RAM and 2 146GB SAS 15K disks on RAID1, per server). The setup will cost me $12,000... I save $5,000 on this hardware deal. I got a really good deal on the hardware, so that's why I decided to buy 4 units, just to plan ahead. Collocation is the way I will go. Nginx will serve the data through an array of 2 servers while the DB will take the other 2.
I post those details not to show off, but to make you understand that I'm very serious about the work I do.
I don't want to be rude but the current approach to implement Sphinx is not good, IMO. I'm talking again about large forums who get hammered daily by a ton of hungry users.