If you're not getting the technical stimulation you desire, that is definitely a good reason to look elsewhere, but here are some other factors I think that are worth considering.
- Do you like your compensation?
- Do you like your job responsibilities and your job overall?
- When other employees have left the company, are they satisfied with their decision and new job?
- Are there other jobs in-house that would be better suited for you?
If you enjoy your job, salary, and the work it entails, you may not want to jump ship. You can find ways to expand your technical horizons on your own or do some contracting on the side. Finding a job you like can be tough, so I put more burden to prove you don't like your current job than you WILL like the next job. Also, I've seen a lot of people leave jobs only to be dissatisfied at the next one and keep job hopping.
On the other hand, if you don't like the work and aren't crazy about the money, then by all means, see what else is out there.
Keep in mind there are MANY things to like or dislike about a job besides just salary: vacation policy, dress code, work hours and flexibility, co-workers, cost of living, the commute, geographical closeness to friends & family, and the list goes on. Make sure you take into account all factors.