If you are looking for an easy to use electric grinder, buy the Northern Tool one for $89. I tried four of the HF ones before I finally gave up on them. I got the Northern Tool version and have been happy with it.
I also file by hand, and I agree you can get sharper chains when filing by hand. But, after about 10 cuts, you really don't notice the difference. Filing by hand is faster, and that's what I do when in the woods. Filing by hand also takes off less metal, so the chain lasts longer.
I have the Dremel guide (actually two of them now - one set up for 3/8" and another set up for 3/8" LP chain). I use these when in the shop just for a quick touch up. Note: if you go the Dremel route, you'll want to invest in some diamond stones. The Dremel ones wear out quickly.
About every 3-5 sharpenings I'll pull the chain off and use the Northern Tool sharpener. At this point I'll also make sure that all of the cutters are the same length, and I'll take down the rakers.
I generally take a file to the chain every other refill on the gas / oil. This keeps it nice and sharp, and actually saves time in the long run. If you know what to look for, you can just keep an eye on your sawdust. Nice big chips and you know the chain is sharp. Smaller chips, time for a touchup. Actual sawdust? Way past due for a sharpening! Time to put it on the electric grinder.