NOTE ON WEIGHTGAINERS
I looked into this more closely (seeing as I bought some yesterday)
Here's what I found:
-Most weightgainers use maltodextrin as a source of carbs
-Maldodextrin is technically not a sugar
-however, Maltodextrin has a GI higher than pure table sugar!!!
Apparently maltodextrin allows weightgainers to claim the carbs are all "complex carbs" while it acts like pure sugar in the system
The best bet is grain-carbohydrates like in driver. However based on my searchings, driver is one of the only MRP/weightgainers that seems to use pure grain carbs

wonder why
Anyway, it seems like a happy medium is fructose. Fructose, despite being a sugar, has a low GI. Although I recall hearing some stuff about fructose following a different energy pathway, one more likely to promote fat gain. Bah.
ANyway, the summary is this:
maltodextrin bad
fructose less bad