Ho much work would it be to convert a Surf to eye dropper?
No work at all, I'd think. It's an all-plastic barrel, no holes. A little silicone grease and an o-ring, and I'm sure you'd be set.
I also was shocked at how small it is the cartridge that comes with it and also the converter. So small!
So I also converted mine with the silicone grease and o-ring (thanks, Goulet pens!), but first I tested the barrel with water for a few days to see if it had any holes or cracks that could let the water spread. Without the o-ring it tends to leak during the writing, but since the moment I converted it properly it's working safe and nicely for some months already.
I'm also keen on those cheap colorful pens.
I also bought mine on e-bay, bought a set of 3 (pastel green, coral and blue). I think it was about US$14 some months ago.
I think it's a nice option for a first pen to people that wants to try a fountain pen but don't want to spend so much money, as with a Lamy Safari, for example (not that Safaris are expensive at all, but you can buy 6 Rotring Surfs by the price of 1 Safari). I really like it.
Parker Vectors are also nice, I bought one at e-bay too, with little leafs patterns. The best part is that they are inexpensive and you will not be sad if the pen is not what you expected. But since I'm glad even with the most bizarre chinese pens, I tend to enjoy the majority of FP in this category. LOL
I feel glad that I'm not the only one...