I'll be in the same boat in a few months. In the meantime, I've been reading the threads on WeldingWeb.com and also on Pirate4x4.com and keeping tabs on the major vendors of the chinese plasmas.
It seems like all the machines are the same, the main factor is the quality of service you get from the vendor in case something goes wrong.
On WeldingWeb, Longevity doesn't seem to have the best rep. They won't discuss warranty issues in public, don't have many favorable threads, and one of the main reps sometimes comes off as arrogant and hostile.
Everlast seems a bit better but they also moderate their forum and close threads that they don't like. It's hard to assess either company, it seems like they promote all the good things said about them and actively try to silence the bad rather than get at the heart of the issue.
Parker is in the same boat as Longevity and Everlast in that they seem to have good products but their customer service is lacking. Phil Sr comes off as a **** (insert your negative word of choice) in many of his responses and has a take it or leave it attitude. While he doesn't close threads or back away from criticism, he does get involved in name calling and other tactics that strike me as childish.
HarborFreight isn't too far off with their pricing and offers the convenience of a storefront. I wouldn't hesitate to buy any warrantied product from them if all else was equal, they've never shied away from replacing a warranty claim. If I had to pick from one of the four companies mentioned above, I'd go with HF.
All that being said, I'll probably go the Hypertherm route when my time comes even though it's a pricier machine. Their rep, JimColt, is all over the messaging boards and ALWAYS gives thought-out, polite, customer oriented replies and is always quick to offer help. The Hypertherm 30 is about $1k which is about $400 more than the Chinese units but if you catch it on sale you can close the price gap even more. It'll cut up to 5/8, is small and lightweight, and has a cult-like following.
In the end, I feel like Hypertherm will be there to help me out 10 years down the road if/when something goes without all the drama that I might get from Longevity, Everlast, or Parker.