RAID 0 is an excellent way to improve transfer rates and read and write speed. Keep in mind that RAID 0 cannot lower seek and access times. For big time use of standard office applications or gaming, the best buy is a single drive with faster access. For other apps such as CAD or video editing, etc., then RAID 0 may be just the thing.
If you want the mirroring affect and add performance at the same time, you are correct in saying the RAID 0+1 is better. Dual level raid, combines multiple mirrored drives (RAID 1) with data striping (RAID 0) into a single array. Provides highest performance with data protection.