How much will learning Ukrainian confuse me later?
I wanted to wait to learn Russian but I have the started the Ukrainian course if for no other reason than to begin learning Cyrillic alphabet. But other than the alphabet, I wonder what will be the value of starting to learn Ukrainian -- is it likely to help me later, or just confuse me?
If you hardly know any Russian, it will feel really weird to switch from Ukrainian to Russian. You might end up speaking a Russian-Ukrainian mixture, which wouldn't be extremely bad since their is a dialect that is like this. Ukrainian is definitely a separate language and should be treated that way (not as strong dialect of Russian). There are many differences between Russian and Ukrainian like: Verb infinitives, spelling, and grammar (7 cases). If you want to learn Russian first, go with Russian, but if you prefer Ukrainian go with Ukrainian.
As a native Russian speaker I'd say that learning Ukrainian would help you. I looked through the Ukrainian course and I found out that a lot of things (at least in the beginning) are similar. Some words are the same in both languages, some have very close pronunciation. Nouns seem to change in cases closely too (however I haven't really looked deep into it). Don't give up Ukrainian, it should help.
I am a non native speaker (formerly fluent but rusty) of Russian learning Ukrainian. IMO, if Russian is what you want to learn, Ukrainian will just confuse you. I'd suggest that you pick one language and stick with it till you have a solid grasp. The alphabet will help some, though they're not the same, and IMO, the two languages are just similar enough to probably be very confusing if you try and learn them simultaneously.
The exception is if you're really good at compartmentalising languages/information, in which case you might be okay.
I'm just a fellow learner, but this is my opinion, anyway!
I'm a native Finnish speaker but used to know Russian quite fluently. I didn't use it for some years and have been now refreshing my skills for about an year. I also started to study Ukrainian.
I think if you are a beginner in both, it would be a better idea to concentrate on either one of the languages instead of learning both at the same time. But if you have already some knowledge, especially grammar and pronounciation at a good level, it is more likely that you won't mix them.
Since I know Russian grammar very well, I can just compare Ukrainian grammar rules to Russian ones and make exceptions when needed. I think I would mix them more easily if I had to study both as completely new.