I think these will do well targeted to parents who are all iPhone who have to get a cheap phone for their kids to take to school. They would have grown up on nokia, use microsoft and these will be an easy sell over something like a huawei or similar priced budget phone. Parents wont buy iPhones for 8-10 year olds and the cheap nasty androids usually suffer because stock android is so aweful compared to the skinned ones, but the cheap low spec skinned androids are too slow.
The UI and MS cloud service use will make windows phone the logical upgrade path. Get them young and lock them in. Genius.
Nokia need to gain back the market share that they lost after sybmian. And I think this is a good move by nokia to get back some users who like android but not the hardware of the current manufacturers. Nokia hardware has been very stable.
Lumia will get them the loyal nokia / windows users and this new X series will most likely get more and more standard users that dont need very flash phones.