In marine systems the majority of problems that occur as a result of poor equipment occur long term. Lets not make any assumptions at all based on 6 months of success. Instead, lets look at the filter based on your goals.
Your aquarium is small, so you have that advantage when it comes to skimming needs. The skilter is, without much debate from hobbyists, the single most ineffective protein skimmer available in the hobby today. The reaction chamber is extremely small, which leads to very little contact time between the bubbles and water. The gallons per hour is sufficient, but this measure is useless unless we are comparing products with similar contact time and bubble quality.
That being said, the skilter can be used effectively depending on what you are intending to keep and what your plans are for water changes and other filtration.
For example, this would be a setup that i would support, using a skilter:
26 gallons, aragonite sand, live rock, 2 Ocellaris Clownfish, and a few extremely hardy soft corals such as Yellow Polyps, Green Star Polyps, and mushrooms.
For another example, this would be a setup that i would not support at all:
26 gallons, aragonite sand, artificial corals, a few small fish, and a couple of inverts.
In other words, it depends completely on your willingness to work within the limits of this filter. My suggestion is to work with the filter you have. You can get your hands we with a marine system and when you are ready to upgrade in tank size then we can talk about real skimmer options.
By the way, you can upgrade the skilter to improve its effectiveness. If you have a small air pump and some airline tubing, then this is very inexpensive. You need to buy a wooden airstone at your LFS. Run airline tubing into the reaction chamber and use the wooden airstone to provide additional air bubbles. This works well on this unit and doubles its efficiency. I ran a 10 gallon system with a skilter 250 using this technique and it was rather effective.
Finally, if you want a more efficient unit now without spending much money at all, consider some of these options available on e-bay: http://cgi.ebay.com/ws/eBayISAPI.dll...m=110262005124 http://cgi.ebay.com/Brand-New-Mini-P...d=p3286.c0.m14 http://cgi.ebay.com/PS-75-Protein-Sk...d=p3286.c0.m14
I like the last option best, because it can move up to a 38 gallon tank or even a 55 gallon fish-only setup. On a 26 gallon it should really kick. I just installed this unit on a friends 29 gallon tank and the results have been very nice.