That is a difficult question indeed, and I don't know if it can be answered without knowing the internals of your company etc.. So I can only give an impression how it was in the companies I worked for.

Generally, there seem to be four aspects:

1. Fun at work

This depends on the team you will work with, and of the kinds of tasks. I prefer design/implementation tasks over testing ... even if I know both can be equally challenging and creative. Working in test automatisation will be mostly working on concepts and implementing them ... but be aware that in case some of your companies projetcs get need/trouble you will be part of the testing-team faster than you can think ;-/
You need to decide for yourself if you'll like that.

2. Career options

In the companies I worked for, there were only few career-options for testers. Developers always have the choice of going the architecture, the requirements of the project-leader way. Tester have only the possibility of leading some testing group. On the other hand, when aiming for a career, some knowledge on testing and automatization is fine. But then prepare yourself to limit your testing-job to 1-2 years, and then change to some other job.

3. Money

If you change inside your company, there is probably no change in salary. In the company I work for, testers tend to earn less than other engineers ... however we tend to have "junior-engineers" as testers and "senior-engineers" as developers (as being part in the test-team is seen as a good way for people to learn about our products before developing them.).

4. Options outside your company

This is probably the "best" aspect of changing to the test-automatization-job. Automatization is a big buzzword, especially when combined with test ... because it promisses cheap and fast tests with high coverage. If you want to change to another job, being an expert in test-automatization is a huge plus (which will probably also have a positive influence on the money-aspect ;-). Be however warned that you will likely stick to the testing-part in future jobs ...

As said in the beginning, it highly depends on you and your situation what the best choice is. And of course my impressions are probably not representative and can be totally different in other companies.

Good luck with your decision!
Rata (interested in the opinion of the other monks)

It's a very different kind of experience from plain old programming (ask me sometime about the week I spent devising and automating adult search tests - two weeks of surfing porm for a living!). If you don't already enjoy writing tests for your own code, you're not going to enjoy doing it for others.

Test automation can be an "in" to an interesting organization that you might not otherwise be considered for. If you do like testing your code and enjoy thinking up new ways to break things, and you like to invent stuff and repurpose things for your own nefarious purposes, or if you like to "run and find out" more than dig in and fix stuff, then test automation may be a good fit for you. A short attention span may actually be a plus.

Also, as the testing person, you have the opportunity to help shape the company's overall development style - things like influencing the adoption of unit testing, of source control, change control, and so on. Remember that automated testing also covers stuff like whether deployments work, whether the code submitted as the release candidate is good, and so on.

Testing can be fantastically rewarding as long as you approach it as something you want to bring all of your ability to; if you look at it as a "second best" then you won't enjoy it or do a good job at it. And if you show talent as a test tool builder, you may find that you're in demand as a programmer in general.