The FormConnect app is compatible with all iPads including the original iPad. However, that does not mean that you should not consider upgrading to the new iPad Air 2 as it includes a faster processor and more memory than previous models.
Faster processors and more memory also helps when you perform searches against large databases (thousands of records) or when you export those records into another format (PDF, CSV, etc.). Don’t forget to factor in the number of photos added to your form. Photos take up a lot of storage space which increases the size of your database when it is exported. This again requires more processing power and memory to handle.