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Sewing in a straight line is only practice, more important is being able to sew parallel to the cut edge with the stitching the correct distance from that edge.
The Singer 201s are greatt workhorses, but they have their limitations; ie only straight stitch. Whilst my go-to machine for patchwork and straight seams is a 201 I wouldn't be without something that can do zig-zag and a few other utility stitches. I also wouldn't want to be without an overlocker with all the stretchy fabrics that are around nowadays.
I have a Singer zig-zagger but it's not that good. On the other hand the Singer buttonholers are brilliant, better than most modern fancy modern machines can do.