The microscope arrived today and I've given it a quick test drive. I bought one like this:
http://cgi.ebay.com/NEW-BINOCULAR-STEREO-MICROSCOPE-20X-30X-40X-60X_W0QQitemZ400082000032QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5d26bed8a0If you don't want to read my entire post, my first impressions of this microscope are very good and I recommend it. Great bang for buck.
The difference between the 30x and th 60x is the extra objective lenses that it comes with. The scope came with two sets: a 10x and a 15x set. Then, there's the primary lens that sits just above the object you're viewing - which can rotate allowing two modes - 2x and 4x. This gives you combinations of 20x,30x,40x and 60x. The big difference between the high magnification modes and lower modes is light gathering and depth of field. The higher the magnification, the less the depth of field and the less light.
This scope has a light that is quite bright (and hot if you accidentally touch it) that gives plenty of warm white light. This scope also has a 2nd light that illuminate the box from underneath for viewing transluscent things/slides, etc. The amount of light loss and depth of field loss does not present a problem, but is noticable.
The first thing I inspected was my iPhone. I was astonished that I could actually peer into the scratches (the 3D effect is amazing - something you don't get in a monoscoping loupe). It's like looking down at your feet and seeing a small ditch. And when you move the focus from the screen, you can "drop down" through the screen surface into the LCD elements on the screen (the screen surface becomes out of focus when the screen's matrix comes into focus). I could see very clear color rectangles that resembled an old Sony triniton tube up close. That kind of 3D depth of field is amazing. The next thing I did was pull a couple hairs out of my head and take a peek. Was akin to looking at a pencit at 12" away from your face, you could actually see the texture of the hair and its sheen.
Very sharp, good feel, good light. Good bargain. Fast shipping. No frills.
What I would expect in more expensive models would be an even focus field across the viewfinder. That is, when the center is in focus, the outsides sometimes aren't, but since you're always tooling with the focus, it's just something you adjust as you look around. For this money, a minor moan.