Pros:
+ Quick to take out, put away, or adjust
+ Inexpensive
+ Can be adjusted low enough for children or short adults
Cons:
- The X-shape gets on the way of your knees
- Visually, an X-stand looks quite busy with all the lines
- While it's sturdy for what it is, it does have a slight "elastic" wobble to it
At 155, I'm very short for an adult and the challenge for people like me is that most stands (and all other furniture for the matter) tend to be a bit too high even at the lowest setting. This is the case especially when you have an electric piano keyboard with piano-like keys so the keyboard adds significant height compared to a less tall synth keyboard. I was easily able to discover the right height for a piano keyboard.
It was usable, but on the long run I found the X-stand's legs a major hindrance because they limited my legroom. Being forced to adjust your proximity to the keyboard not by what's a comfortable distance to play from but by where your knees won't hit the stand is a recipe for a short person's ergonomics problem simply changing shape.
I used this with Roland RD-64, and while the stand is very sturdy for what it is, it does have a slight wobble when playing. I believe this is probably the case with all X-stands because of the design. The issue is amplified if you're playing on an uneven floor (partial carpets etc) although one of the leg covers has a rotatable part that can compensate for uneven surfaces.
It's certainly good for what it is, but you have to understand what it's for. I needed a stand for an electric piano that sits in one place and never goes on the road or gets packed away. I would say that because of the poor leg ergonomics, the wobble, and the busy look, don't cheap out by buying an X-stand; instead, get a proper stand that's shaped like a table because it will give you the required legroom, it will be absolutely steady, it will look nice, and you might be able to expand it with stand accessories such as extra tiers, microphone stands sheet music stands.
What an X-stand excels at is portability and how ready it is even if you don't keep it in position at all times; you'll want one of these when you need to frequently take it with you, to store it away, or if you play synthesizer parts rather than sit at your piano rehearsing whole musical pieces for hours at a time.