I've used the HF once and hated it. The blades were horrible and they kept coming loose. It produces a bit more noise as well, but that is splitting hairs. For the price though, it's hard to argue the value.
I have a Fein that gets used about once every other month (DIY) and I'm happy with it, but the price (even today) is a bit steep. If I was buying today, I'd have a hard look at the others on the market. Case in point is the Porter Cable PCE605K. $118 on Amazon, 3 amp motor, and 2.8 degree oscillation angle outguns the Fein on paper. They also advertise tool-less blade change. I haven't used it, but at 60% of the cost, I would bet it would do everything I ask of it.
I would recommend the tool-less blade change. I'm constantly repositioning the blades so I can hold the tool at a good angle to have the most control (to get a clean cut). The one time I used an HF, I wasted more time fiddling with the blade than I did actually cutting, and when the bolt backed itself out, that just pissed me off.
To answer your other question, Bosch sells an adaptor called "OIS" which will adapt their blades to several other major brands of oscillating tools (Fein is among them). I love this since it allows me to run down to my local big box and grab a Bosch blade at the last minute (this was before Sears started hawking Fein). I don't think this adaptor will work with the PC tool though. I don't have any experience with PC's blades so I can't speak to their quality. I believe they are made in China, where many of the Bosch blades are Swiss.
Another option is the 18V Makita, which has a 4 degree oscillating angle (equivalent to the professional Fein models). If you're not using the tool continuously, perhaps cordless might be an option? I've been using their 18V system (not an oscillating tool though) for 6+ years now and I've been very pleased with the durability of their batteries. But, as I said, if you plan to use the tool continuously for more than 5 mins at a clip, cordless may not be the best solution. I'm also not sure about blade compatibility with this tool, so that's something to look into.