It's just a flouroscent fixture- no better or worse than a shoplight so be careful and don't overpay.

It would be adequate light for a small tray of houseplants and/or understory tropicals, and not enough for any light demanding species or large collections. So it depends on what you have and how many.

I was thinking of getting something similar to this as well, but from what you say and everything else I am reading here on this forum, now I think I should just purchase regular florescent shop lights, which are definately alot less expensive.

Now there are some fixtures (bulb included) on sale at my local hardware store - the bulbs say F18T8W and 18W - I am assuming this is a low wattage and won't be bright enough for plants that like bright yet indirect light? And isn't it a must to have warm and cool bulbs for the best light?

The wattage of you light is (nearly) irrelevant. What matters is how much light you have per square foot. A small light is OK for lighting a small area, but you need a large light for a large area. In all cases, you should use suitable reflectors or baffles to keep the light on the plants and not bouncing off into the room.

Generally I don't recommend the 24" fluorescent tubes, they are quite inefficient compared to the 48" tubes and cost virtually as much, sometimes more. That inefficiency means you will struggle to get enough light onto the area they cover and they will only be suitable for seedlings and low light plants.

Mixing warm and cool white fluorescents is one way to go, or just use the cool whites. Just make sure you don't have only warm whites, that isn't so good.

Rats! What I have now is warm whites, two of them that are 24"! However, they are in a small area. I don't have anything to keep the light from reflecting, but I don't have much under them either, just a few cuttings and small plants.
Thank you, I understand more now what I will need to upgrade and for when I get the new ones.