if your looking for something with that feature, a TomTom would probably work a little bit better, however, i do see a fair of those come back into the stores (they freeze up alot..)
a TomTom 910 will be the most similar GPS to a Nuvi350, and you will also get a 20gb HD, European maps, and its a bulkier unit...
i can check on monday if the Nuvi 600 series GPS will let you fiddle with the routes..haven't spent much time with them