Simple test to show that node-redis corrupts data if the data contains special chars.

nodeRedisBreaks.js

var redis = require('redis-node');
var redcli = redis.createClient();
redcli.select(1);

var testObj = {'a': 'ö'}
var jsonString = JSON.stringify(testObj);
console.log('Origin JSON string: '+jsonString);
console.log('JSON.parse(jsonString): ');
console.log(JSON.parse(jsonString));
redcli.set('testJson', jsonString, function(err, status) {
	if (err) throw err;

	if (status) {
		redcli.get('testJson', function(err, jsonStringFromRedis) {
			if (err) throw err;

			if (jsonStringFromRedis) {
				console.log('\nRedis JSON string: '+jsonStringFromRedis);
				try {
					JSON.parse(jsonStringFromRedis);
				} catch(e) {
					console.log('JSON.parse(jsonStringFromRedis) fails since output is corrupted.\n');
				}
			}
		});
	}
});

// Ugly hack to format output easily.
setTimeout(function() {
	var testStr = 'ä';
	console.log('Origin test string: '+testStr);

	redcli.set('testStr', testStr, function(err, status) {
		if (err) throw err;

		if (status) {
			redcli.get('testStr', function(err, testStrFromRedis) {
				if (err) throw err;

				if (testStrFromRedis) {
					console.log('Redis test string: '+testStrFromRedis);
				}
			});
		}
	});
}, 150);

output

Origin JSON string: {"a":"ö"}
JSON.parse(jsonString): 
{ a: 'ö' }

Redis JSON string: {"a":"ö"
JSON.parse(jsonStringFromRedis) fails since output is corrupted.

Origin test string: ä
Redis test string: �

Try this
In particular, the major change is:
var buf = new Buffer(32),
size = buf.write(testStr, 0, "utf8");
testStr = buf.slice(0, size);

I think testing for multi-byte characters on all incoming data to the libraray from INSIDE redis-node will sacrifice speed/performance.
It might be better for each user to determine the intent of the input string/buffer and act accordingly

Thoughts?

var redis = require('redis-node');
var redcli = redis.createClient();
redcli.select(1);

var testObj = {'a': 'ö'}
var jsonString = JSON.stringify(testObj);
console.log('Origin JSON string: '+jsonString);
console.log('JSON.parse(jsonString): ');
console.log(JSON.parse(jsonString));
redcli.set('testJson', jsonString, function(err, status) {
  if (err) throw err;

  if (status) {
    redcli.get('testJson', function(err, jsonStringFromRedis) {
      if (err) throw err;

      if (jsonStringFromRedis) {
        console.log('\nRedis JSON string: '+jsonStringFromRedis);
        try {
          JSON.parse(jsonStringFromRedis);
        } catch(e) {
          console.log('JSON.parse(jsonStringFromRedis) fails since output is corrupted.\n');
        }   
      }   
    }); 
  }
});

// Ugly hack to format output easily.
setTimeout(function() {
  var testStr = 'ä';
  console.log('Origin test string: '+testStr);

  var buf = new Buffer(32),
      size = buf.write(testStr, 0, "utf8");
  testStr = buf.slice(0, size);
  redcli.set('testStr', testStr, function(err, status) {
    if (err) throw err;

    if (status) {
      redcli.get('testStr', function(err, testStrFromRedis) {
        if (err) throw err;

        if (testStrFromRedis) {
          console.log('Redis test string: '+testStrFromRedis.toString("binary"));
        }   
      }); 
    }   
  }); 
}, 150);