As far as I know, HMX-1 doesn't fly UH-1's. Only CH-46's, CH-53's, UH/VH-60's, and VH-3's. As Flash said, they do a lot of OT&E stuff and their motto is "Service to the Fleet." Good motto, considering how they've driven a part to me (a fleet guy) when I had to land in a farmer's field, and they could get me the part quicker than the fleet could (I was about a 2 hour drive from Quantico).
As Harrier Dude said, it's a highly competitive process to get into the "X". We had a number of pilots in my squadron that came from HMX-1 and they filled me in on how the process worked. Your reputation in the fleet counts for alot. You get 4 year orders to HMX-1, and they refer to them as freshman-senior years. Your freshman and sophomore year are spent "green side". You fly 46's, 53's, and 60's (that are painted green from top to bottom), doing OT&E and filling out frags that the fleet can't support (most of the TBS/IOC frags are flown by HMX). Your junior and senior years are spent "white side". That's when you're flying VH-60's & VH-3's (white on the top and green on the bottom). You may or may not fly the president, but you will fly a lot of VIP's. Every pilot spends two years green side, and two years white side. Since there's a chance to fly the president, you have to qualify for a Yankee White clearance. If you can't, you won't go there as a pilot.
Also, from what I've been told (one of the Maj's in my squadron was trying to get me to sign up for the X) everyone quals on everything. When you're green side, you'll be qual'd on 46's, 53's, and 60's - but most of your flying will be in what you fly in the fleet (i.e. a Phrog guy would fly the Phrog 2/3 of the time, and the other 1/3 would be split between 60's and 53's). The only thing that sucks about the deal is that you're gone for something like 300 days out of the year... And a lot of the guys at HMX-1 are tools.
You almost had me wanting to fly helos...almost.