I've used
Futurehosting since 2008. They have excellent support. However they use Virtuozzo. It's not CPU abuse that's the problem, as FH has well-managed systems that are not overloaded (like OpenVZ often is), but Parallel's VM layer can be screwy. Back in 2009, Virtuozzo ate my VPS. I had backups, and always do, so it wasn't a problem, just a nuisance with 4+ days downtime. As time moves on, I wish they'd adopt Xen or KVM instead. Because they're one of the best hosts you'll use.
Downtownhost had a major snafu in early (Q1) 2012, though they've since redeemed themselves. It's smaller than Futurehosting, so you'll often see the owner answering support tickets -- not that it's a bad thing. What I like about DTH is they use Xen for the VMs. And they are a good host with upgrade paths, from shared to reseller to VPS to dedicated.
Wiredtree is more expensive than the others, which is why I rank them lower than the others. Support is great, but not really any different from DTH and maybe not as good as FH. And again, Virtuozzo. It works great, but when you do have issues, it tends to be the virtualization's fault and not the host. It's another hosts that I wish would adopt Xen or KVM instead; it just works better.
And I say all this being hyper-critical. Each of these is an excellent host, and you'll be hard-pressed to find ones who are better.
Since I know you know about hosting, you got the somewhat advanced answers.
