One of the most common questioned I get asked at seminars is "are plug-ins worth it?" (or slight variations on that theme). My answer? Usually something along the lines of "most of the time" or "it depends".
Before I go any further, let me add that what I'm going to write here is an opinion on how how decide if a plug-in is right for you - this is not a review or recommendation of specific plug-ins
First, what do we mean by plug-ins? (Veteran Photoshop users can skip again here). Plug-ins are add-on software programs that you install (plug in) to Photoshop to enhance its performance, either by improving upon a Photoshop function or by offering a feature not found in the program.
So how do you determine if a plug-in tool is going to be "worth it" for you?
I see three basic categories of plug-ins:
1. Tools that are simply better than Photoshop.
One example would be noise removal plug-ins. The Reduce Noise filter in Photoshop works well, but plug-ins such as Noiseware Professional or Dfine just work better. That's not just my opinion, anyone who has used a third party noise reduction tool will tell you that these products are better. So in this case, if you come across noise problems with any regularity, the purchase of a extra tool that will improve your photos will be well worth it.
Another example is a tool to enlarge your images. While the Image Size command does a good job in making images larger, add-on tools such as Genuine Fractals is generally accepted as doing a better job.
So if your work requires noise removal or enlarging images, these plug-ins are easy to justify.
2. Tools that can be more efficient than Photoshop
One example of this category would be masking software. Yes, with a bit of practice (and [shameless plug] online training courses or a DVD on Selections [/shameless plug]) you can get pretty good at making selections and masks. Do the masking plug-ins give you a better end result? Sometimes, but very often they will do the job in less time, so if you spend a fair bit of your time making selections and masks, then a plug-in that saves you even 10 - 20% of your time adds up pretty quickly.
Another example of this type of plug-in is PhotoFrame. Yes, I can make cool edges for my photos pretty easily (I even wrote a book on the subject). But, PhotoFrame gives me tons of built-in frames and the ability to experiment in ways that are so much more efficient than creating "by hand". (I created a collection of frames that are in PhotoFrame so of course I going to be a fan of this plug-in!)
3. Tools that add extra functions or take things to another level
These plug-ins may be the hardest to justify a purchase, because they often do things that are rather unique or specialized, or because at first glance they're not that different from Photoshop. Examples here would be any plug-in that does special effects, 3D, color enhancement, black and white conversions, etc. My advice here is to talk to people that use them, read reviews and take advantage of free trial versions. For example, for the rare occasions that I create and print black and whites, I'm happy with the results I get from Photoshop. However, I hear lots of people talking about Silver Efex Pro from Nik Software and what a great job it does. For me, I'm not sure that I would purchase a plug-in for black and white conversion - but if you do that a lot and this tool gives you more control, takes less time or gives you results you like better than Photoshop, then it would be worth it.
Can you see my dilemma it answering the question "are plug-ins worth it?" There is no easy answer.
There are a number of plug-ins that have become an important part of my work - in some cases I would find it difficult to not use them. I guess to sum things up I would ultimately answer the question this way. If a plug-in saves you time, go for it. If a plug-in gives you - in your opinion - better results, buy it. Remember, most plug-in companies offer free trials, so be sure to take advantage of that and try before you buy.