When you need to make curved cuts, particularly on plywood, particle board or other relatively thin materials, few power tools are as handy as a jigsaw. While jigsaws have been maligned in the woodworking community for their propensity for their blades to bend, resulting in a cut that is not square, the risks are manageable. The possibility of an angled cut should not prevent you from adding one of these versatile, portable power tools to your workshop.
Features to Look For
Expensive jigsaws feature primarily two main features that account for their added cost: Orbital Action and Variable Speed. A standard action jigsaw will move the jigsaw blade solely in an up-and-down motion, where an orbital-action jigsaw will angle the blade slightly forward and into the stock on the up-swing. The angle of the action can typically be adjusted for different types of materials and can minimize wear on the saw blade. In many materials, this will make for a smoother cut.
Second, higher-end jigsaws will feature variable speeds. While this isn't always necessary when woodworking, it is especially useful if the jigsaw is used to cut metals. I do find it helpful, however, to be able to slow the blade speed down when making some rather intricate cuts and feel that this feature is well worth the extra cost. If you get used to a variable-speed jigsaw and are forced to switch to a single-speed model, you'll miss the ability to adjust cutting speeds.
Some additional features to look for include a splinter control shoe, which is a small insert on the shoe of the jigsaw, that will help keep splintering to a minimum. You may also find a trigger lock, that will allow you to lock the jigsaw to a particular speed, and dust collection. I personally don't find the dust collection features of jigsaws of much use, but this is a matter of personal preference.
Depth of Cut
Most jigsaws will cut up to 2-inches of depth in woodworking applications, and approximately 1/2-inch on metal. Some jigsaws may feature a slightly deeper cut, but this isn't necessarily desirable on a jigsaw, as the deeper the action, the better the chance of the blade bending and breaking.
Because jigsaws blades have a tendency to bend, particularly on thicker stock, you may end up with an undesirable angled cut. To combat this, avoid cutting directly up to your cut line. Instead, it is advisable to leave a bit of material next to the line (1/8" should be acceptable), and then use an oscillating drum sander to finish to the line. This will minimize any risk of ending up with less-than-desired results of your jigsaw cuts.
Corded vs. Cordless Jigsaws
Some manufacturers now offer cordless jigsaws, which are not nearly as powerful as their corded counterparts. This difference in power is definitely noticed, as cordless jigsaws don't cut nearly as quickly or handle as thick of stock as a corded model. As such, I'd avoid the cordless jigsaws.
Some units called Scroll Saws have a blade steering knob on top of the unit that allows the blade to turn while cutting (rather than turning the entire jigsaw). The problem with scroll saws is that pressure must be consistently kept behind the blade to keep the cut consistent, which can be difficult to control when the knob is turned to a sharp angle. As such, I find this to be a control that really isn't necessary, and even counter-productive in certain situations.
While extra features are certainly nice to have, I find that the only extra feature I really would want to invest in is the variable speed. I like the orbital action models, but don't find their added cost is typically necessary considering the investment. I'd rather put that extra money in the piggy bank and save for a band saw.