THIS IS WHAT IT DOES:
1. 3/4-thread overlock (uses 4 threads; best for use with knits or upholstery fabric)
2. 3-thread overlock (general use) in two widths - 3mm (using only the right needle) and 5mm (using only the left)
3. Rolled hem (great for edges of napkins, pajama bottoms, frilly skirts, etc)
4. Flatlock stitch (decorative or flat seams)
5. Blind hem
THIS IS WHAT IT DOESN'T DO:
1. Coverlock stitch (stretchy stitch with two straight lines on the front of the fabric). If you're sewing for yourself (i.e. not selling what you make), you can fake this stitch on your regular zigzag sewing machine with a twin needle. It's not quite the same, but close enough for me.
2. Chain stitch (a semi-straight stitch, similar to a regular sewing machine but easier to rip out (i.e. good for basting) and a good reinforcement for upholstery)
Other sergers I looked at that did the coverlock stitch in addition to overlock, etc. had complicated and time consuming adjustments to be made to switch to the coverlock. If you're going to use it a lot, consider getting a separate machine that does it (the Brother model is 2340CV).
The one feature the 1034D is missing for me is the ability to do a 3-thread overlock and a chain stitch at the same time - good for upholstery but something available only on a 5 thread machine. Brother 1034D
5) Nice little things:
1. You have the option of using regular thread spools (cheaper and smaller if you don't need 1000 yards x 4 of whatever color you're buying)
2. You use regular needles - so you can use them in both your regular sewing machine and your serger
3. It's really easy to control speed with the foot pedal - very responsive
4. Disabling the knife (that trims your fabric as you sew) is done with just the flick of a switch
5. Differential feed allows you to sew any thickness of fabric, line up stripes evenly, etc.