Ever since Slicehost got bought, I've been less and less impressed with them - their customer service isn't as responsive as it used to be, and they seem to have spent more time rewriting their support chatroom than making any improvements to the actual service that they offer. If you're looking for the same thing(but cheaper), Rackspace's Cloud Servers is essentially a re-branded version of Slicehost. You end up paying $10/mo for the same system, except that outgoing bandwidth is no longer bundled - but until you're pushing >40GB of bw/month, Cloud Servers will be cheaper for the same thing.
If you're okay paying the price for Slicehost's services, Linode did better than both of them in this benchmark: http://journal.uggedal.com/vps-performance-comparison
, and offers more resources at the same price point - but your mileage may vary.