I like to keep my 1800 no lower than 2500 rpm when riding on anything other than level ground. My absolute minimum is 2,000 rpm. Pulling a slight incline, depending on what gear you're in could cause a small vibration until the engine reaches its happy torque zone for the load on it.
If it's just a slight vibration I wouldn't worry about it. Just keep an ear on it so that you notice if it gets worse.
Wing with Roadsmith kit, Traxxion Ak20 cartridges and Accuride System.
07 ST 1300 for two-wheeled fun!
3,000 is a good happy medium for shifting up.
Vibration may be early signs of u-joint going south.